162
6 Nanomaterials for Batteries
Zn − 2e
−
+ 2OH
−
→ ZnO + H 2 O ϕ
0
a = −1.245 V
(6.8)
The cathode reaction when the battery discharges:
O 2 + 4e
−
+ 2H 2 O → 4OH
−
ϕ
0
c = 0.401 V
(6.9)
Battery reaction:
2Zn + O 2 → 2ZnO E
0
cell = 1.646 V
(6.10)
Zinc is not easily eroded with the appropriate inhibitors in the electrolyte, and
remains so stable that zinc-air batteries have become a concern of everyone in the
world. The zinc-air battery has lots of advantages like the self-discharge rate, excellent energy density, stable capacity, terrific safety, low raw material cost, and environmental protection (Li et al. 2013). Zinc-air batteries have been commercialized
successfully for many years. Initially, these products were large batteries using alkaline electrolytes. They were used in railway signaling, long-distance communication,
and marine navigation devices requiring long-time and low-rate discharges. With the
development of thin-layer electrode technology, this technology has been applied to
small button batteries and high capacity primary batteries such as hearing aids, along
with similar applications. The expanding of electric vehicles contributes to provide a
vast space for development of zinc-air batteries during recent years. Zinc-air battery
has significant advantages in terms of performance and cost. Based on various factors,
we believe that despite the need to further improve the zinc-air battery, it is also very
likely to become one of the best choices for the electric bicycle power supply, and
has a far-reaching development prospect.
6.4.5.2 Aluminum-Air Battery
Aluminum is a cheap, lightweight metal, and has a higher electrode potential as an
electrode material (Fig. 6.11). However, aluminum has a severe hydrogen evolution
corrosion problem in an alkaline electrolyte, resulting in a low anode efficiency and
hindering the commercial popularization of aluminum-air batteries. Therefore, the
anode electrode material of the aluminum-air battery is an aluminum alloy, which is
continuously consumed and generates Al(OH) 3 during battery discharge; the positive
electrode is an oxygen electrode and ingests oxygen in the air; potassium hydroxide
(KOH), sodium hydroxide (NaOH) or sodium chloride (Na) aqueous solution as
electrolyte. Aluminum ingests oxygen in the air and generates a chemical reaction
when the battery is discharged, and aluminum and oxygen react to convert it into
alumina. Al-air batteries have made rapid progress and have achieved good results
in EV applications, and are a kind of promising air batteries.
The aluminum alloy electrode continuously reacts with OH
− in the electrolyte to
form Al(OH) 4
− and emits electrons. The electrons flow into the air electrode (positive
electrode) through the external line load, and the air electrode acquires electrons and
6 Nanomaterials for Batteries
Zn − 2e
−
+ 2OH
−
→ ZnO + H 2 O ϕ
0
a = −1.245 V
(6.8)
The cathode reaction when the battery discharges:
O 2 + 4e
−
+ 2H 2 O → 4OH
−
ϕ
0
c = 0.401 V
(6.9)
Battery reaction:
2Zn + O 2 → 2ZnO E
0
cell = 1.646 V
(6.10)
Zinc is not easily eroded with the appropriate inhibitors in the electrolyte, and
remains so stable that zinc-air batteries have become a concern of everyone in the
world. The zinc-air battery has lots of advantages like the self-discharge rate, excellent energy density, stable capacity, terrific safety, low raw material cost, and environmental protection (Li et al. 2013). Zinc-air batteries have been commercialized
successfully for many years. Initially, these products were large batteries using alkaline electrolytes. They were used in railway signaling, long-distance communication,
and marine navigation devices requiring long-time and low-rate discharges. With the
development of thin-layer electrode technology, this technology has been applied to
small button batteries and high capacity primary batteries such as hearing aids, along
with similar applications. The expanding of electric vehicles contributes to provide a
vast space for development of zinc-air batteries during recent years. Zinc-air battery
has significant advantages in terms of performance and cost. Based on various factors,
we believe that despite the need to further improve the zinc-air battery, it is also very
likely to become one of the best choices for the electric bicycle power supply, and
has a far-reaching development prospect.
6.4.5.2 Aluminum-Air Battery
Aluminum is a cheap, lightweight metal, and has a higher electrode potential as an
electrode material (Fig. 6.11). However, aluminum has a severe hydrogen evolution
corrosion problem in an alkaline electrolyte, resulting in a low anode efficiency and
hindering the commercial popularization of aluminum-air batteries. Therefore, the
anode electrode material of the aluminum-air battery is an aluminum alloy, which is
continuously consumed and generates Al(OH) 3 during battery discharge; the positive
electrode is an oxygen electrode and ingests oxygen in the air; potassium hydroxide
(KOH), sodium hydroxide (NaOH) or sodium chloride (Na) aqueous solution as
electrolyte. Aluminum ingests oxygen in the air and generates a chemical reaction
when the battery is discharged, and aluminum and oxygen react to convert it into
alumina. Al-air batteries have made rapid progress and have achieved good results
in EV applications, and are a kind of promising air batteries.
The aluminum alloy electrode continuously reacts with OH
− in the electrolyte to
form Al(OH) 4
− and emits electrons. The electrons flow into the air electrode (positive
electrode) through the external line load, and the air electrode acquires electrons and