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CN-121978559-A - Method for judging whether NP ratio of lithium ion battery is better and application thereof

CN121978559ACN 121978559 ACN121978559 ACN 121978559ACN-121978559-A

Abstract

The invention relates to the technical field of battery detection, and discloses a method for judging whether NP ratio of a lithium ion battery is good or not and application thereof. The fresh lithium battery is charged to 100% of SOC at constant current, the negative electrode potential V neg of the battery at 100% of SOC is measured, and whether V neg meets the formula V neg epsilon [ k+a ] is calculated (C IR), wherein IR is the internal resistance of the battery at 100%, wherein the unit is omega, C is the current during charging, the unit is A, a is the measurement error parameter, the range is 0.9-1.1, k is the equilibrium potential when the cathode completely intercalates lithium, if satisfied, the NP of the battery is better, and if not satisfied, the NP of the battery is less than good. The method is simple and convenient to operate, can be used for judging whether the design of the battery is reasonable and whether the quality of the battery is good, and has important significance for the design and the manufacture of the battery.

Inventors

  • SHAO JINXIAO
  • YANG HANQING
  • LIANG TING
  • Yang Yishuang
  • YANG QINGHENG

Assignees

  • 江苏中兴派能电池有限公司

Dates

Publication Date
20260505
Application Date
20260325

Claims (8)

  1. 1. A method for determining whether an NP ratio of a lithium ion battery is preferred, comprising: Charging a fresh lithium battery to 100% soc at constant current; Measuring the negative electrode potential V neg at 100% SOC of the battery, and calculating whether V neg meets the formula V neg E [ k+a ] (C IR), wherein IR is the internal resistance of the battery at 100%, the unit is omega, C is the current during charging, the unit is A, a is the measurement error parameter, the range is 0.9-1.1, and k is the equilibrium potential when the cathode completely intercalates lithium; If so, the NP of the battery is better, and if not, the NP of the battery is less than optimal.
  2. 2. The method according to claim 1, wherein the negative active material of the fresh lithium battery is graphite or hard carbon, k is an equilibrium potential when the graphite or hard carbon negative electrode is fully intercalated with lithium, and the value is 0.03-0.05 v.
  3. 3. The method of claim 1, further comprising resting the fresh battery fresh lithium battery in a 23-27 ℃ environment for 2-3 hours before charging it to 100% soc.
  4. 4. The method of claim 1, wherein fresh lithium batteries are charged to 100% soc at a constant current of 0.2-0.5 c.
  5. 5. The method of claim 1, wherein the positive active material of the lithium battery is at least one of lithium iron phosphate, lithium manganate, and lithium cobaltate.
  6. 6. The method according to claim 1, wherein the three-electrode reference electrode used for testing the negative electrode potential V neg is prepared by leading an unoxidized copper wire between the internal diaphragms of the battery as a reference electrode, welding the copper wire on the polished nickel sheet, and then plating a lithium layer on the copper wire.
  7. 7. The method of claim 6, wherein the method of plating the lithium layer on the copper wire comprises connecting the negative electrode of the battery to the positive electrode clamp of the charging and discharging cabinet, connecting the reference electrode to the negative electrode clamp of the charging and discharging cabinet, and charging for 2-4 hours at a constant current of 0.01-0.02 mA.
  8. 8. Use of the method according to any of claims 1-7 in the design and manufacture of batteries.

Description

Method for judging whether NP ratio of lithium ion battery is better and application thereof Technical Field The invention relates to the technical field of battery detection, in particular to a method for judging whether NP ratio of a lithium ion battery is good or not and application thereof. Background The NP ratio of the lithium ion battery refers to the ratio of the actual capacity of the negative electrode of the battery to the actual capacity of the positive electrode, is a core parameter of the battery design, and is generally larger than 1, and the NP ratio is essentially that lithium loss caused by film forming reaction in the first charge-discharge process of the battery in the formation stage is balanced through the 'surplus capacity of the negative electrode', and meanwhile, the generation of negative electrode lithium dendrite is avoided. If the NP ratio is too small, the capacity of the negative electrode is insufficient, all lithium ions released by the positive electrode cannot be inserted into the negative electrode in the charging process, redundant lithium ions are precipitated on the surface of the negative electrode to form lithium dendrites, active lithium can be continuously reduced, the cycle life is greatly reduced, the diaphragm can be pierced by continuous growth of the lithium dendrites, direct contact of the positive electrode and the negative electrode is caused, short circuit is formed in the battery, thermal runaway risks are caused, and potential safety hazards are caused. If the NP ratio is too large, the capacity of the negative electrode is redundant, although potential safety hazards are avoided, the negative electrode plate is thickened by excessive active materials of the negative electrode, the overall thickness and weight of the battery are increased, the volume energy density and the weight energy density of the battery are directly reduced, the transmission path of lithium ions is increased by excessive negative electrode plates, the internal resistance of the battery is increased, the high rate performance of the battery is possibly affected, and in addition, the production efficiency and the cost of battery manufacturing are reduced due to excessive active materials of the negative electrode. Therefore, too large or too small an NP ratio causes a series of problems, and it is an important problem how to judge whether the NP ratio of the battery is suitable. In view of this, the present application has been made. Disclosure of Invention The invention aims to provide a method for judging whether the NP ratio of a lithium ion battery is better or not and application thereof, wherein the lithium intercalation degree of a negative electrode and the potential of the negative electrode are related to determine the optimal NP ratio of the lithium ion battery, and the operation is simple. The invention is realized in the following way: in a first aspect, an embodiment of the present invention provides a method for determining whether an NP ratio of a lithium ion battery is better, including: Charging a fresh lithium battery to 100% soc at constant current; Measuring the negative electrode potential V neg at 100% SOC of the battery, and calculating whether V neg meets the formula V neg E [ k+a ] (CIR), wherein IR is the internal resistance of the battery at 100%, the unit is omega, C is the current during charging, the unit is A, a is the measurement error parameter, the range is 0.9-1.1, and k is the equilibrium potential when the cathode completely intercalates lithium; If so, the NP of the battery is better, and if not, the NP of the battery is less than optimal. In an alternative embodiment, the negative active material of the fresh lithium battery of the fresh battery is graphite or hard carbon, k is an equilibrium potential when the graphite or hard carbon negative electrode completely intercalates lithium, and the value is 0.03-0.05V. In an alternative embodiment, the fresh lithium battery is left to stand in an environment of 23-27 ℃ for 2-3 hours before charging the fresh lithium battery to 100% soc. In an alternative embodiment, fresh lithium batteries are charged to 100% soc at a constant current of 0.2-0.5 c. In an alternative embodiment, the positive active material of the lithium battery is at least one of lithium iron phosphate, lithium manganate and lithium cobaltate. In an alternative embodiment, the three-electrode reference electrode used in testing the negative electrode potential V neg is manufactured by leading an unoxidized copper wire between the internal diaphragms of the battery as a reference electrode, welding the copper wire on a polished nickel sheet, and then plating a lithium layer on the copper wire. In an alternative embodiment, the method for plating the lithium layer on the copper wire comprises the steps of enabling the negative electrode of the battery to be connected with the positive electrode clamp of the charging and discharging c