Lithium-ion batteries work principle

Lithium-ion battery: It is a secondary battery (rechargeable battery) that mainly relies on lithium ions moving between the positive and negative electrodes to work. During charge and discharge, Li+ is intercalated and deintercalated between the two electrodes: when charging, Li+ is deintercalated from the positive electrode, and the electrolyte is embedded in the negative electrode, and the negative electrode is in a lithium-rich state;

Lithium batteries are classified into lithium batteries and lithium ion batteries. Both mobile phones and laptops use lithium-ion batteries, which are commonly referred to as lithium batteries. The battery generally uses a lithium-containing material as an electrode and is representative of modern high-performance batteries. True lithium batteries are rarely used in everyday electronics because of their high risk.

The lithium-ion battery was first developed by Sony Corporation of Japan in 1990. It is to insert lithium ions into carbon (petroleum coke and graphite) to form a negative electrode (lithium for lithium batteries or lithium alloys for conventional lithium batteries). The positive electrode material is commonly used for LixCoO2, LixNiO2, and LixMnO4, and LiPF6+diethylene carbonate (EC) + dimethyl carbonate (DMC) for the electrolyte.

Petroleum coke and graphite as non-toxic materials are non-toxic and have sufficient resources. Lithium ions are embedded in carbon, which overcomes the high activity of lithium and solves the safety problems of traditional lithium batteries. The positive LixCoO2 can reach the charge and discharge performance and life. The higher the level, the lower the cost, and the overall performance of the lithium-ion battery is improved. It is expected that lithium-ion batteries will occupy a large market in the 21st century.

The reaction formula for charging and discharging lithium ion secondary batteries is LiCoO2+C=Li1-xCoO2+LixC

Lithium-ion batteries are easily confused with the following two types of batteries:

(1) Lithium battery: Metal lithium is used as a negative electrode.

(2) Lithium-ion battery: A non-aqueous liquid organic electrolyte is used.

(3) Lithium ion polymer battery: a polymer is used to gel a liquid organic solvent, or an all-solid electrolyte is directly used. Lithium-ion batteries generally use a graphite-based carbon material as a negative electrode.

The lithium ion battery uses a carbon material as a negative electrode and a lithium-containing compound as a positive electrode, and no lithium metal exists, and only lithium ions. A lithium ion battery is a general term for a battery in which a lithium ion intercalation compound is used as a positive electrode material. The charging and discharging process of a lithium ion battery is a process of intercalating and deintercalating lithium ions. In the process of intercalation and deintercalation of lithium ions, concomitant insertion and deintercalation of equivalent electrons with lithium ions (commonly referred to as embedding or deintercalation of the positive electrode and insertion or deintercalation of the negative electrode). During charge and discharge, lithium ions are intercalated/deintercalated and inserted/deintercalated between the positive and negative electrodes, and are aptly referred to as "rocking chair batteries".

Lithium-ion batteries have high energy density and high average output voltage. Self-discharge is small, less than 10% per month. There is no memory effect. The operating temperature range is -20 ° C ~ 60 ° C. Excellent cycle performance, fast charge and discharge, charging efficiency up to 100%, and high output power. long lasting. Without environmental pollution, it is called a green battery.

A "lithium battery" is a type of battery using a lithium metal or a lithium alloy as a negative electrode material and using a nonaqueous electrolyte solution. Lithium metal batteries were first proposed and studied by Gilbert N. Lewis in 1912. In the 1970s, M.S. Whittingham proposed and began researching lithium-ion batteries. Due to the very active chemical properties of lithium metal, the processing, storage and use of lithium metal are very demanding on the environment. Therefore, lithium batteries have not been used for a long time. With the development of science and technology, lithium batteries have become the mainstream.

Lithium batteries can be roughly divided into two categories: lithium metal batteries and lithium ion batteries. Lithium-ion batteries do not contain metallic lithium and are rechargeable. The fifth-generation lithium-metal battery of rechargeable batteries was born in 1996, and its safety, specific capacity, self-discharge rate and performance price ratio are better than lithium-ion batteries. Due to its own high technical requirements, only a few companies in the country are producing such lithium metal batteries.

Lithium metal battery:

A lithium metal battery is generally a battery using manganese dioxide as a positive electrode material, metallic lithium or an alloy metal thereof as a negative electrode material, and a nonaqueous electrolyte solution.

Basic principle of lithium battery

Basic principle of lithium battery

Discharge reaction: Li+MnO2=LiMnO2

lithium ion battery:

A lithium ion battery is generally a battery using a lithium alloy metal oxide as a positive electrode material, graphite as a negative electrode material, and a nonaqueous electrolyte.

The reaction that occurs on the charged positive electrode is

LiCoO2==Li(1-x)CoO2+XLi++Xe-(electron)

The reaction occurring on the charging negative electrode is

6C+XLi++Xe-=LixC6

Rechargeable battery total reaction: LiCoO2+6C=Li(1-x)CoO2+LixC6

Positive

Cathode material: There are many optional cathode materials, and most of the mainstream products use lithium iron phosphate. Different cathode material comparisons:

LiCoO2

3.7V

140mAh/g

Li2Mn2O4

4.0V

100mAh/g

LiFePO4

3.3V

100mAh/g

Li2FePO4F

3.6V

115mAh/g

Positive electrode reaction: Lithium ions are embedded during discharge, and lithium ions are deintercalated during charging. When charging: LiFePO4→Li1-xFePO4+xLi++xe-discharge: Li1-xFePO4+xLi++xe-→LiFePO4.

Negative electrode

Anode material: Graphite is mostly used. New research has found that titanate may be a better material.

Negative electrode reaction: Lithium ions are deintercalated during discharge, and lithium ions are embedded during charging.

When charging: xLi++xe-+6C→LixC6

When discharging: LixC6→xLi++xe-+6C

Lithium batteries were first used in pacemakers. The lithium battery has a very low self-discharge rate and a flat discharge voltage, so that the pacemaker implanted in the human body can operate for a long time without recharging. Lithium batteries generally have a nominal voltage higher than 3.0 volts, making them more suitable for use as integrated circuit power supplies. Manganese dioxide batteries are widely used in calculators, digital cameras, and watches.

In order to develop more excellent varieties, various materials have been studied to create an unprecedented product.

In 1992, Sony successfully developed lithium-ion batteries. Its practicality has greatly reduced the weight and volume of portable electronic devices such as mobile phones, notebooks, and calculators.

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