阅读说明：本技术 锂离子电容器的预锂化方法 (Prelithiation method for lithium ion capacitor ) 是由 娄凤柳 于 2020-04-02 设计创作，主要内容包括：本发明涉及一种用于使锂离子电容器电极预锂化的方法,其中该方法包括将锂离子(5)吸附到活性炭电极表面；通过将活性炭电极和负极组装在电解液中来构建锂离子电容器；组装后,通过对锂离子电容器充电来使阳极锂化。(The invention relates to a method for prelithiating an electrode of a lithium ion capacitor, wherein the method comprises adsorbing lithium ions (5) to the surface of an activated carbon electrode; constructing a lithium ion capacitor by assembling an activated carbon electrode and a negative electrode in an electrolyte; after assembly, the anode is lithiated by charging the lithium ion capacitor.)

1. A method for prelithiating a lithium ion capacitor, the method comprising the steps of:

-adsorbing lithium ions on an activated carbon electrode;

-constructing a lithium ion capacitor by assembling an activated carbon electrode and a negative electrode in an electrolyte; and

after assembly, the anode is lithiated by charging the lithium-ion capacitor.

2. The method of claim 1, wherein the step of adsorbing lithium ions on the activated carbon electrode comprises reducing an electrochemical potential of the activated carbon electrode in an electrolyte containing lithium ions.

Technical Field

The invention relates to a prelithiation method of a lithium ion capacitor.

Background

Lithium ion (Li-ion) capacitors are hybrid systems that integrate a lithium ion battery negative electrode (e.g., graphite) and a supercapacitor positive electrode (typically activated carbon). Therefore, they exhibit high specific power, good cycling stability and moderate specific energy, and thus have a wide range of potential applications. However, prelithiation of the anode with lithium ions is a prerequisite step to lower the anode potential, thereby widening the operating voltage window and increasing the specific energy. Various methods have been proposed for prelithiation of lithium ion capacitor anodes. They can be classified into three groups, i.e., a method using lithium metal, a lithium-containing compound, or lithium ions.

US 6862168B 2 discloses the use of a sacrificial metallic lithium electrode, which is partially or completely dissolved during the first charge. The disadvantage is that an expensive metal foil with through holes is required as a current collector to let the lithium ions pass through. Furthermore, the prelithiation process is very slow.

Stabilized lithium metal particles have also been used for prelithiation. Lithium carbonate (Cao, W.J.and J.P.Zheng, Li-ion capacitors with carbon cathode and hard carbon/stabilized lithium metal powder electrode. journal of Power Sources,2012.213: p.180-185) or lithium hexafluorophosphate (US 2017/0062142A 1 and US 2014/0146440A 1) has been coated on the surface of lithium metal particles to prevent it from reacting with oxygen. However, a drying chamber is still required to process the stabilized lithium metal particles.

Lithium-containing compounds have also been used as lithium sources for prelithiation of lithium ion capacitors. Kim and co-workers (Park, m. -s., et al., a Novel Lithium-copper anode for an Advanced Lithium Ion capacitor, 2011.1(6): p.1002-1006.) use a Lithium transition metal oxide mixed with activated carbon as a positive electrode, thereby supplying Lithium cations to the negative electrode in the first charging step. Therefore, the specific energy of the battery is reduced. During the subsequent discharge, the transition metal oxide cannot be lithiated again. The delithiated metal oxide will remain in the positive electrode as an electrochemically inert material. Therefore, the specific energy of the battery is reduced.

Recently, f.beguin and colleagues ((r))P, et al, Safe and recyclable lithium-ion batteries using a crystalline organic lithium salt, nature Materials,2017) employs a mixture of a sacrificial organic lithium salt and activated carbon as the positive electrode. The lithium salt is oxidized and lithium cations are released to the negative electrode upon first charging. The oxidized salt dissolves into the electrolyte. However, the proposed salt is sensitive to air, which makes it difficult to handle.

The lithium salt in the electrolyte is also considered to be a source of pre-lithiated lithium. Beguin and colleagues used a specific charging protocol to supply the negative electrode with lithium cations (Khomenko, v., E) in the electrolyte.and F.B, gun, High-energy dense graph/AC capacitor in organic electrolyte. journal of Power Sources,2008,177(2): p.643-651). Stefan et al prelithiate the negative electrode by oxidizing the lithium salt in the electrolyte (US 2015/0364795 a 1). The lithium salt generally has limited solubility in organic solvents, and thus may reduce the conductivity of the electrolyte, thereby reducing the specific power.

US 2002/0122986 a1 discloses storing lithium ions in a separator made of molecular sieves to compensate for lost lithium ions in a lithium ion battery, thereby extending the service life of the lithium ion battery. But the commercial application cost is too high and the lithium ion storage capacity is also very limited.

US2018197691a1 discloses another method of making a lithium ion capacitor.

While all of these methods are effective or partially effective for prelithiation of lithium ion capacitor negative electrodes, they all have their drawbacks. The known methods can not simultaneously meet the requirements of high efficiency, low cost, safe operation and no obvious side effect.

It is an object of the present invention to remedy or reduce at least one of the disadvantages of the prior art, or at least to provide a useful alternative to the prior art. This object is achieved by the features specified in the following description and in the appended claims. The invention is defined by the independent patent claims, while the dependent claims define advantageous embodiments of the invention.

Disclosure of Invention

In a first aspect, the present invention more particularly relates to a method of prelithiating a lithium ion capacitor, wherein the method comprises the steps of adsorbing lithium ions on an activated carbon electrode; assembling an activated carbon electrode and a negative electrode in an electrolyte to construct a lithium ion capacitor; the anode is lithiated after assembly by charging the lithium ion capacitor. When adsorbed on activated carbon, lithium ions can be incorporated into the lithium ion capacitor in a safe, efficient and controlled manner, and without introducing unwanted additional materials. The anode material may include, for example, graphite, hard carbon, soft carbon, metal alloys, silicon oxide, metal oxides, carbon nanotubes, carbon nanofibers, graphene, or any combination thereof.

In one embodiment, the step of adsorbing lithium ions onto the activated carbon electrode may comprise reducing the electrochemical potential of the activated carbon electrode in an electrolyte containing lithium ions. This can be achieved, for example, by discharging the activated carbon-containing cell (in which activated carbon serves as the positive electrode) or charging the activated carbon-containing cell (in which activated carbon serves as the negative electrode). Such a lithium ion adsorption process may be performed in a bath-to-bath (bath) manner or a continuous manner. In this way, positively charged lithium ions will be adsorbed onto the activated carbon to improve adsorption.

During the step of lithiating the anode by charging the lithium ion capacitor after assembly, lithium ions from the activated carbon will move through the electrolyte towards the anode. Prelithiation of the anode has the effect of lowering the anode potential to allow for higher output voltages of the lithium ion capacitor. If the anode contains graphite, for example, lithium ions may be intercalated into the graphite, which results in a decrease in the potential. The degree of reduction in the anode potential due to prelithiation may vary slightly from anode material to anode material.

The invention also relates to a prelithiation lithium ion capacitor comprising a negative electrode, an activated carbon electrode and an electrolyte, wherein prelithiation of the lithium ion capacitor can be obtained using the method according to the first aspect of the invention.