Since
the lithium-ion battery entered the market, it has been widely used due
to its advantages such as long life, large specific capacity and no
memory effect. Low-temperature use of lithium-ion batteries has problems
such as low capacity, severe attenuation, poor cycle rate performance,
obvious lithium evolution, and unbalanced lithium extraction. However,
with the continuous expansion of application areas, the restrictions
brought by the low-temperature performance of lithium-ion batteries have
become more and more obvious.
The
discharge capacity of lithium-ion batteries at -20°C is only about
31.5% of that at room temperature. The operating temperature of
traditional lithium-ion batteries is between -20 and +55°C. However, in
the fields of aerospace, military industry, and electric vehicles,
batteries are required to work normally at -40°C. Therefore, improving
the low-temperature properties of lithium-ion batteries is of great significance.
Factors restricting the low-temperature performance of lithium-ion batteries
1.
In a low temperature environment, the viscosity of the electrolyte
increases, or even partially solidifies, resulting in a decrease in the
conductivity of the lithium ion battery.
2.
The compatibility between the electrolyte and the negative electrode
and the separator becomes poor in a low temperature environment.
3.
Under low temperature environment, lithium ion battery's negative
electrode is severely precipitated lithium, and the precipitated metal
lithium reacts with the electrolyte, and the product deposition causes
the thickness of the solid electrolyte interface (SEI) to increase.
4.
In the low temperature environment, the diffusion system of the lithium
ion battery inside the active material decreases, and the charge
transfer resistance (Rct) increases significantly.
Discussion on the decisive factors affecting the low-temperature performance of lithium-ion batteries
Opinion 1:
The electrolyte has the greatest impact on the low-temperature
performance of lithium-ion batteries, and the composition and physical
and chemical properties of the electrolyte have an important impact on
the low-temperature performance of the battery. The problems faced by
the battery cycle at low temperatures are: the viscosity of the
electrolyte will increase, the ion conduction speed will slow down, and
the electron migration speed of the external circuit will not match, so
the battery will be severely polarized and the charge and discharge
capacity will drop sharply. Especially when charging at low temperature,
lithium ions can easily form lithium dendrites on the surface of the
negative electrode, causing battery failure.
Opinion 2: The main factor limiting the low-temperature performance of lithium-ion batteries is the sharply increased Li+ diffusion resistance at low temperatures, not the SEI film.
Therefore, in order to ensure the low temperature performance of lithium-ion batteries, the following points need to be done:
(1) Form a thin and dense SEI film;
(2) Ensure that Li+ has a large diffusion coefficient in the active material;
(3) The electrolyte has high ionic conductivity at low temperatures.
BENZO Energy Technology Co.,Ltd
UFine Technology Co., Ltd
Site: www.bz-battery.com / www.benzoenergy.com
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