Small li-ion rechargeable batteries

1. Small li-ion rechargeable batteries
1-1 Structure of small li-ion rechargeable batteries for use in devices where L and W
dimensions are limited.
The table below provides an overview of the SLB.

Table 1-1. Product specifications
Category

Function

Product number

SLB03070LR35

Nominal capacity*

0.35mAh

ESR@1kHz*

Max. 12Ω

12Voltage

Current
Temperature

Average operating voltage

2.4V

Maximum charging voltage

2.8V

Minimum discharge voltage

1.8V

Maximum charging current

7mA

Maximum discharging current

7mA

Operational temperature range-30°C to +60°C

Storage temperature range-30°C to +60°C* Nominal capacity measurement direction(1) Pre-discharging: Discharging at 1C (0.35mA) to thelower-limit voltage of 1.8V
(2) Charging: After charging at 1C (0.35mA) to theupper-limit voltage of 2.8V, constant-voltage
charging* at 2.8V
*Constant-voltage charging occurs until nominal
capacity x 5% (mA) is reached.
(3) Resting: 30 minutes(4) Discharging: Discharging at 1C (0.35mA) to thelower-limit voltage of 1.8* ESR measurement direction:(1) Pre-discharge: Discharging at 1C (0.35mA) to thelower- limit voltage of 1.8V
(2) Charging: After charging at 1C (0.35mA) to 2.4V,charging at rated capacity x 5% (mA) at 2.4V
(3) Measuring: AC impedance measurement used tocheck actual resistance at 1kHz

1[Winding element]

2[Product exterior]
Lead
Cathode Separate※

Anode[Product dimensions]Size

φD0L0φdP

φ3×7L

3.1±0.1

6.8+0.2/-0.1

0.40±0.05

1.0±0.3

Figure 1-1. Shape and dimensions of small li-ion rechargeable batteries
Small Li-Ion Rechargeable Batteries Technical Notes CAT. 8601

Small li-ion rechargeable batteries

1-2 Materials in small li-ion
rechargeable batteries
Small li-ion rechargeable batteries are manufactured byapplying the electrode technology utilized in Toshiba
TMCorporation’s SCiB rechargeable batteries. The
most distinctive feature in the design of our small liion rechargeable batteries is the use of lithium titanate(Li 4 Ti 5 O 12 ) rather than graphite as the anode active
material. As is discussed in “2. Features of small li-ionrechargeable batteries”, The selection of the optimal
electrolyte and separator combined with the lithium
titanate electrode is key to realizing the battery’s superior
functionality.
The cathode and anode reactions during charging
and discharging of small li-ion rechargeable batteries isdescribed below.
In electric double-layer capacitors, the electrodesurface and ions in the electrolyte form an electric
double layer that forms the energy storage mechanism.
By comparison, small li-ion rechargeable batteries use
an electrochemical storage mechanism that utilizes
electrochemical reactions. Battery capacity is realized
through the adsorption and release of lithium ions in theelectrodes. Self-discharge is limited as a result.
Standard lithium-ion rechargeable batteries use
electrolytes comprised of lithium salts dissolved in an
organic solvent. The lithium ions in the electrolytes remainsuspended in the organic solvent. When a designatedvoltage is applied, the lithium ions migrate, resulting inthem becoming stacked within the anode.
On the surface of the anode’s active material is a solid
electrolyte interphase (SEI) coating—a compound inwhich electrolytes undergo reductive decomposition andpossess high lithium conductivity. As Figure 1-2 shows,when the anode undergoes the electrochemical reaction,
the disassociated lithium ions pass through the SEI
coating and begin to stack up.

coatings are formed. An effective way to form a thin SEI
coating is to select anode materials that have a reaction
potential higher than the electrolyte’s decomposition rate.
Graphite is typically used as the anode material forstandard lithium-ion rechargeable batteries. The potential
for reaction with the lithium ions is extremely small, at 0.1V
vs. Li/Li+, which is one reason for the decomposition ofelectrolytes, and the formation of thick SEI coatings., This
results in higher levels of resistance. By contrast, using
lithium titanate in the anodes the lithium ions reaction
voltage is 1.55V vs. Li/Li+, Reactions at a higher potential
result in the formation of a thin SEI coating that reduces
electrolyte decomposition. The lower resistance means
fewer lithium ions are consumed in the electrolyte, andsuperior life properties are acheived.
Optimizing the electrode, separator, and electrolyte
results in superior high-temperature tolerance and cyclelife performance. Using highly safe active materials resultsin superior product safety.

Figure 1-2. Reaction mechanism on the anode oflithium-ion rechargeable batteries

However, the passage of lithium ions through theSEI coating on the surface of the anode active material
generates significant resistance, and that resistancebecomes larger as SEI coatings grow thicker. In addition,
lithium ions are consumed in the electrolyte when SEI
Small Li-Ion Rechargeable Batteries Technical Notes CAT. 8601