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JP-7855714-B2 - Electrochemical apparatus and electronic apparatus including the same

JP7855714B2JP 7855714 B2JP7855714 B2JP 7855714B2JP-7855714-B2

Inventors

  • 崔輝
  • 劉俊飛
  • 唐超
  • 韓軍強

Assignees

  • 寧徳新能源科技有限公司

Dates

Publication Date
20260508
Application Date
20220328

Claims (11)

  1. An electrochemical apparatus, It includes a positive electrode and an electrolyte, The electrolyte comprises ethylene carbonate, propylene carbonate, and succinonitrile. The positive electrode includes a positive electrode active material. The positive electrode active material contains metal element A, The aforementioned metal element A includes at least one of Mg, Zr, and Al. When the mass content of succinonitrile is a%, the mass content of ethylene carbonate is b%, and the mass content of propylene carbonate is c%, and k is set to k = b/c, then a and k satisfy 1.25 ≤ k ≤ 6 and a/k ≥ 0.2, and When the mass content of the metal element A is x% relative to the mass of the positive electrode active material, x satisfies 0.01 ≤ x ≤ 1. The electrochemical apparatus wherein the electrolyte further contains lithium difluorophosphate, and when the mass content of lithium difluorophosphate is d% of the mass of the electrolyte, d satisfies 0.01 ≤ d ≤ 0.5, and x and d satisfy 0.05 ≤ d/x ≤ 25 .
  2. The electrochemical apparatus according to claim 1, wherein x and k satisfy x/k ≤ 0.4.
  3. The electrochemical apparatus according to claim 1, wherein x and a satisfy 0.001 ≤ x/a ≤ 1.
  4. The electrochemical apparatus according to claim 1, wherein the positive electrode active material contains lithium cobalt oxide.
  5. The electrochemical apparatus according to claim 1, wherein the positive electrode active material contains lithium nickel-cobalt-manganate.
  6. The positive electrode active material comprises lithium cobalt oxide and lithium nickel cobalt manganese oxide. The electrochemical apparatus according to claim 1, wherein when the ratio of the mass of lithium cobalt oxide to the mass of lithium nickel cobalt manganese oxide is g, g satisfies 1 ≤ g ≤ 9 with respect to the mass of the positive electrode active material, g satisfies 1 ≤ g ≤ 9.
  7. The electrochemical apparatus according to claim 1, wherein when the median diameter Dv50 of the positive electrode active material is y μm, y satisfies 2 ≤ y ≤ 25.
  8. The electrochemical apparatus according to claim 7, wherein x and y satisfy 10 ≤ y/x ≤ 900.
  9. The electrochemical apparatus according to claim 7, wherein y and a satisfy 1 ≤ y/a ≤ 36.
  10. The electrochemical apparatus according to claim 1 , wherein k and d satisfy 0.00 6 ≤ d/k ≤ 0.4.
  11. An electronic apparatus comprising an electrochemical apparatus according to any one of claims 1 to 10 .

Description

This invention relates to the field of energy storage, and more specifically, to electrochemical devices and electronic devices including them. Rechargeable electrochemical devices are considered one of the most attractive energy storage systems due to their advantages such as high energy density, relatively simple reaction mechanisms, high operating voltage, long lifespan, and environmental friendliness. Currently, electrochemical devices such as lithium-ion batteries are widely used in various fields, including wearable devices, smartphones, drones, and laptop computers. The following describes in detail embodiments of the present invention. These embodiments should not be construed as limiting the present invention. As used in this invention, the terms “include,” “encompass,” and “contain” are used in their open and non-restrictive sense. In this specification, quantities, ratios, and other numerical values may be expressed in range form. It should be understood that such range forms are used for convenience and conciseness. It should be flexibly understood that such range forms include not only numerical values explicitly designated as range limits, but also all individual numerical values or subranges included within the above range, such that each numerical value and subrange is explicitly designated. In the embodiments and claims for carrying out the invention, a list of items connected by the terms “one or more of,” “one or more of,” “at least one of,” or other similar terms means any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means A only, B only, or A and B. In other examples, if items A, B, and C are listed, the phrase “at least one of A, B, and C” means A only, B only, C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, and C. Item A may contain one or more elements. Item B may contain one or more elements. Item C may contain one or more elements. The electrolyte, as a crucial component of an electrochemical apparatus, is used to transport lithium ions between the positive and negative electrodes and to achieve continuous intercalation and release of lithium ions in the materials of the positive and negative electrodes, thereby enabling the apparatus to perform its charge and discharge functions. Therefore, the electrolyte is essential for the electrochemical apparatus to achieve excellent high-temperature characteristics. One of the main features of the electrolyte described in this invention is that the electrolyte simultaneously contains ethylene carbonate (EC), propylene carbonate (PC), and succinonitrile (SN). When the mass content of succinonitrile is a%, the mass content of ethylene carbonate is b%, and the mass content of propylene carbonate is c%, and k is defined as k = b/c, then a and k satisfy the conditions 1.25 ≤ k ≤ 6 and a/k ≥ 0.2. The present invention proposes the above-mentioned electrolyte because it has been found that adding a certain amount of ethylene carbonate to the electrolyte can improve the high-voltage withstand voltage characteristics and high-temperature stability of the electrolyte itself. However, if the ethylene carbonate content in the electrolyte is too high, gas generation becomes serious, which is detrimental to the high-temperature interval cycle characteristics. In contrast, propylene carbonate has excellent high-temperature stability, and its addition can compensate for the defects of ethylene carbonate. Therefore, by adding both ethylene carbonate and propylene carbonate to the electrolyte, the high-temperature stability of the electrolyte itself can be improved, thereby improving the high-temperature interval cycle characteristics and high-temperature cycle characteristics of the electrochemical apparatus. Furthermore, by adding a nitrile compound to the electrolyte, the transition metal in the positive electrode active material (for example, metallic cobalt in lithium cobalt oxide) can be effectively stabilized, reducing the elution of the transition metal and stabilizing the structure of the positive electrode active material, thereby further improving the cycle stability and high-temperature characteristics of the electrochemical apparatus. Here, the effect of adding succinonitrile (SN) to the electrolyte is particularly remarkable compared to other nitrile compounds. This is because the cyano group in the succinonitrile structure coordinates with metal ions in the positive electrode active material to form complexes, reducing side reactions between the positive electrode active material and the electrolyte, thereby decreasing gas generation inside the electrochemical apparatus. Furthermore, the cyano group reacts with water or hydrogen fluoride in the electrolyte, enhancing the cycle stability of the electrolyte and further improving the high-temperature cycle characteristics of the electrochemical apparatus. However, the present invention