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Preparation method of composite lithium metal anode

A lithium metal negative electrode and metal negative electrode technology, which is applied in the field of preparation of composite lithium metal negative electrodes, can solve the problems of lithium metal irreversible capacity loss, reduce battery safety, and reduce battery cycle life, so as to inhibit the growth of lithium dendrites and improve cycle life. Stability, effect of reducing chalking

Inactive Publication Date: 2018-08-03
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] However, the lithium metal negative electrode has not been able to achieve large-scale commercial application. The main reason is that it is easy to grow and form dendritic or mossy lithium dendrites during the charging process of lithium metal batteries, that is, the deposition process of lithium metal, which will give lithium metal The battery brings the following problems: (1) The growth of a large number of dendrites will greatly increase the interface area between metal lithium and electrolyte, forming a large number of surface passivation salt layers, which will bring irreversible capacity loss to metal lithium; (2) Dendrite growth is easy Piercing the separator causes the internal short circuit of the battery and reduces the safety of the battery; (3) the dendrites will dissolve unevenly during the discharge process, thereby forming "dead lithium" that is separated from the negative electrode current collector, reducing the available capacity of the negative electrode; (4) a large number of "dead lithium" The accumulation of "lithium" and the surface passivation salt layer will pulverize the metal lithium negative electrode and expand the volume of the entire negative electrode sheet, destroying the cycle stability of the battery and greatly reducing the cycle life of the battery
Among them, the easiest method for pre-preparing metal lithium is to directly deposit metal lithium into the framework material by electroplating in the electrolyte. However, further research has found that metal lithium deposited by electroplating contains a large amount of impurities in the passivation salt layer, making the obtained The effective lithium content of the composite material is extremely low, which cannot meet the performance requirements of high stability and high specific capacity of the lithium metal negative electrode
Afterwards, the researchers imagined that pouring molten liquid metal lithium directly into the framework material could obtain a composite negative electrode containing high-purity lithium metal, thereby effectively solving the problem of lithium content. Lithium affinity, unable to directly absorb metallic lithium into the framework

Method used

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preparation example Construction

[0016] A kind of preparation method of composite lithium metal negative electrode provided by the invention, it specifically comprises the following steps:

[0017] 1) modifying the surface of the framework material of the lithium metal negative electrode to make a framework material with a lithium-friendly surface;

[0018] 2) Heating solid lithium to 190°C to 1330°C to mix metallic lithium with a framework material having a lithium-friendly surface, the mixing method includes one of direct contact, ultrasonic, oscillation, shearing, stirring or fluidization methods or Multiple types; and then cooled to form a composite lithium metal negative electrode, so that the mass fraction of metal lithium in the composite negative electrode is 40% to 95%.

[0019] The framework material is a conductive framework material or an insulating framework material, and the conductive framework material is one or more of graphene, carbon nanotubes, carbon fibers, copper, nickel, aluminum, iron ...

Embodiment 1

[0022] Embodiment 1: Get graphene powder and put into tube furnace, pass into H 2 with NH 3 2:1 mixed gas, nitrogen doping reaction at a constant temperature of 600 ° C for 1 hour to make nitrogen-doped graphene with a nitrogen doping amount of 2 atomic percent, and press the nitrogen-doped graphene into a 500 μm thick self-supporting pole piece. Put the pole piece into 400°C molten metal lithium in an argon atmosphere. The molten lithium can be poured into the nitrogen-doped graphene skeleton by itself. After taking out and cooling, a composite lithium metal negative electrode material with an average lithium metal mass fraction of 82% is obtained. The composite lithium metal negative electrode material was matched with the lithium iron phosphate positive electrode to assemble a full battery for testing, and the electrolyte was lithium hexafluorophosphate, ethylene carbonate and diethyl carbonate solutions. Under 1C rate, the battery can be cycled stably for more than 500 c...

Embodiment 2

[0023] Embodiment 2: put into the magnesia template that is loaded with Fe catalyst in tube furnace, pass into H 2 、CH 4 with NH 3 The 2:7:1 mixed gas was kept at 900 °C for 5 hours to prepare in-situ nitrogen-doped carbon nanotubes. The obtained powder is impregnated and stirred by adding excess mass fraction of 10% dilute hydrochloric acid to dissolve and remove the Fe catalyst and magnesium oxide template, and the insoluble matter is filtered, washed and dried to obtain nitrogen-doped carbon nanotube powder. Melt the powder and metal lithium block at 190° C. in an argon atmosphere, and fully stir to make the molten lithium and nitrogen-doped carbon nanotube powder fully mix, and obtain nitrogen-doped carbon nanotube powder filled with metal lithium after cooling. The obtained powder was pressed into tablets to prepare a composite lithium metal negative electrode material with a thickness of 500 μm and a mass fraction of lithium metal of 40%. The composite lithium metal n...

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Abstract

The invention discloses a preparation method of a composite lithium metal anode and belongs to the technical field of lithium metal batteries. The preparation method of the composite lithium metal anode comprises steps as follows: firstly, the surface of a framework material is modified, the framework material with the lithiophilic surface is prepared, the framework material is contacted with liquid metal lithium, so that the liquid metal lithium is injected into the framework material with the lithiophilic surface, and the composite lithium metal anode is prepared after cooling. The lithiophilic surface can be obtained through modification of various framework materials (including a conductive framework material and an insulated framework material), the framework materials are efficientlycomposited with the liquid metal lithium, and the composite lithium metal anode material is obtained. When the obtained composite lithium metal anode material is assembled in a total battery, growthof lithium dendrites can be effectively inhibited, the volume expansion effect of the anode is relieved, the pulverization phenomenon of the lithium metal anode is reduced, and the cycling stability and the safety of the lithium metal battery are substantially improved, and the cycle life of the lithium metal battery is substantially prolonged.

Description

technical field [0001] The invention relates to a preparation method of a composite lithium metal negative electrode, belonging to the technical field of lithium metal batteries. Background technique [0002] With the rapid development of notebook computers, smart phones, drones, electric vehicles and other industries, secondary batteries such as lithium-ion batteries, which are widely used today, are difficult to meet the increasing demand for energy storage systems in today's society. Finding safer electrode materials with higher energy density has become the key to the current secondary battery research. Thanks to the extremely high theoretical specific capacity of lithium metal (3860mAh g -1 ) and the lowest redox electrode potential (-3.040V vs. standard hydrogen electrode), the lithium metal anode has become the most promising anode material for next-generation secondary batteries. [0003] However, the lithium metal negative electrode has not been able to achieve la...

Claims

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Application Information

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IPC IPC(8): H01M4/36H01M4/38H01M4/62H01M4/1395H01M10/052
CPCH01M4/1395H01M4/362H01M4/382H01M4/628H01M10/052Y02E60/10
Inventor 张强张睿程新兵
Owner TSINGHUA UNIV
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