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EP-4163994-B1 - NEGATIVE ELECTRODE FOR RECHARGEABLE LITHIUM BATTERY AND RECHARGEABLE LITHIUM BATTERY INCLUDING SAME

EP4163994B1EP 4163994 B1EP4163994 B1EP 4163994B1EP-4163994-B1

Inventors

  • SEOL, Jongheon
  • Kim, Minjae
  • KIM, Soochan
  • JUNG, Hyeseung
  • CHO, CHAEWOONG
  • HONG, MINYOUNG
  • NAM, JUNGHYUN
  • HAN, Sungsoo

Dates

Publication Date
20260506
Application Date
20221006

Claims (7)

  1. A negative electrode (20) for a rechargeable lithium battery (100), comprising: a current collector; and a negative active material layer on the current collector and comprising a negative active material and a conductive material, wherein the negative active material comprises a silicon-based active material, the conductive material comprises carbon nanotubes, and wherein the negative active material and the conductive material are comprised in the negative active material layer in order to satisfy a relationship of Equation 1 and Equation 2: 26 < A * B − C * D / 10 < 55 600 ≤ D ≤ 1000 in Equations 1 and 2, A is wt% of the silicon-based active material comprised in the negative active material layer, B is a specific surface area (m 2 /g) according to a BET method specified by ISO 9277:2010 of the silicon-based active material comprised in the negative active material layer, C is wt% of carbon nanotubes comprised in the negative active material layer, and D is a specific surface area (m 2 /g) according to a BET method specified by ISO 9277:2010 of the carbon nanotubes comprised in the negative active material layer, wherein the silicon-based active material comprises a composite of Si and carbon.
  2. The negative electrode for a rechargeable lithium battery of claim 1, wherein the specific surface area according to a BET method specified by ISO 9277:2010 of the silicon-based active material is 1 m 2 /g to 20 m 2 /g.
  3. The negative electrode for a rechargeable lithium battery of claim 1, wherein an amount of the negative active material is 95 wt% to 99.99 wt% based on total, 100 wt% of the negative active material layer.
  4. The negative electrode for a rechargeable lithium battery of claim 1, wherein an amount of the carbon nanotubes is 0.01 wt% to 5 wt% based on the total, 100 wt% of the negative active material layer.
  5. A method of preparing a negative electrode (20) for a rechargeable lithium battery (100), comprising the steps of: distributing a conductive material in a solvent; adding a negative active material to the distributed liquid to prepare a composition for a negative active material layer; and coating and drying the composition for the negative active material layer on a current collector to obtain the negative active material layer, wherein the conductive material comprises carbon nanotubes, the negative active material comprises a silicon-based active material, and the negative active material and the conductive material are comprised in the negative active material layer in order to satisfy a relationship of Equation 1 and Equation 2: 26 < A * B − C * D / 10 < 55 600 ≤ D ≤ 1000 in Equations 1 and 2, A is wt% of the silicon-based active material comprised in the negative active material layer, B is a specific surface area (m 2 /g) according to a BET method specified by ISO 9277:2010 of the silicon-based active material comprised in the negative active material layer, C is wt% of carbon nanotubes comprised in the negative active material layer, and D is a specific surface area (m 2 /g) according to a BET method specified by ISO 9277:2010 of the carbon nanotubes comprised in the negative active material layer, wherein the silicon-based active material comprises a composite of Si and carbon.
  6. The method of preparing a negative electrode for a rechargeable lithium battery of claim 5, wherein the dispersed liquid comprising the conductive material has a concentration of 0.1 wt% to 5 wt%.
  7. A rechargeable lithium battery (100), comprising: a negative electrode (20) of any one of claim 1 to claim 4; a positive electrode (10); and an electrolyte.

Description

BACKGROUND OF THE INVENTION (a) Field of the Invention It relates to a negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the same. (b) Description of the Related Art Recently, the rapid spread of electronic devices such as mobile phones, laptop computers, and electric vehicles using batteries require surprising increases in demands for rechargeable batteries with relatively high capacity and lighter weight. Particularly, a rechargeable lithium battery has recently drawn attention as a driving power source for portable devices, as it has lighter weight and high energy density. Accordingly, researches for improving performances of rechargeable lithium are actively being undertaken. A rechargeable lithium battery includes a positive electrode and a negative electrode which may include an active material being capable of intercalating and deintercalating lithium ions, and an electrolyte, and generate electrical energy due to an oxidation and reduction reaction when lithium ions are intercalated and deintercalated into the positive electrode and the negative electrode. As for a positive active material of a rechargeable lithium battery, transition metal compounds such as lithium cobalt oxides, lithium nickel oxides, and lithium manganese oxides are mainly used. As the negative active material, a crystalline carbonaceous material such as natural graphite or artificial graphite, or an amorphous carbonaceous material, is used. Nowadays, the negative active material layer has been thickly formed in order to improve the energy density of the rechargeable lithium battery, and especially, there is attempted to prepare a negative active material layer in the form of double layer using the silicon-based active material. For example EP 3 678 228 A2 discloses a negative electrode including: a current collector for a negative electrode; a first negative electrode active material layer positioned on at least one surface of the current collector for a negative electrode and containing a carbonaceous active material; and a second negative electrode active material layer positioned on the first negative electrode active material layer and containing a silicon-based active material and carbon nanotubes. A lithium secondary battery including the negative electrode is also disclosed. However, this causes problems such as breakdown of the negative electrode due to the volume expansion and shrinkage of the silicon-based active material during charging and discharging. CN105576185A discloses a negative electrode according to the state of the art for a rechargeable lithium battery comprising a current collector, and a negative active material layer on the current collector and comprising a negative active material and a conductive material, wherein the negative active material comprises a silicon-based active material, the conductive material comprises carbon nanotubes, and the silicon-based active material comprises a composite of Si and carbon. SUMMARY OF THE INVENTION It was object of the present invention to provide a negative electrode for a rechargeable lithium battery exhibiting high energy density and cycle-life characteristics. Another object of the present invention was to provide a rechargeable lithium battery including the negative electrode. The present invention is directed to a negative electrode as defined in claim 1. The negative electrode includes a current collector and a negative active material layer on the current collector and including a negative active material and a conductive material The negative active material includes or consists of a silicon-based active material and the conductive material includes or consists of carbon nanotubes, wherein the negative active material and the conductive material are included in the negative active material layer in order to satisfy a relationship of Equation 1 and Equation 2. 26<A*B−C*D/10<55 600≤D≤1000 (In Equations 1 and 2, A is wt% of the silicon-based active material included in the negative active material layer,B is a specific surface area (m2/g) according to a BET method specified by ISO 9277:2010 of the silicon-based active material included in the negative active material layer,C is wt% of carbon nanotubes included in the negative active material layer, andD is a specific surface area (m2/g) according to a BET method specified by ISO 9277:2010 of the carbon nanotubes included in the negative active material layer, wherein the silicon-based active material comprises a composite of Si and carbon. The specific surface area according to gas adsorption of the silicon-based active material may be about 1 m2/g to about 20 m2/g. An amount of the negative active material may be about 95 wt% to about 99.99 wt% based on a total, 100 wt%, of the negative active material layer. An amount of the carbon nanotubes may be about 0.01 wt% to about 5 wt% based on the total, 100 wt%, of the negative active material layer. According t