CN-116754620-B - Quantitative evaluation device and method for stability of lithium ion solid electrolyte

CN116754620BCN 116754620 BCN116754620 BCN 116754620BCN-116754620-B

Abstract

A quantitative evaluation device and method for stability of lithium ion solid electrolyte comprises an upper hydraulic plate of a press, a press probe, an upper polar post, a sample sleeve, a lower polar post and a lower hydraulic plate of the press, wherein the upper polar post and the lower polar post are sequentially arranged from top to bottom, binding posts are respectively arranged on the upper polar post and the lower polar post, a sample to be tested is placed in the sample sleeve, a pressure gauge connected with the press probe, an electrochemical workstation respectively connected with the binding posts of the upper polar post and the binding post of the lower polar post, and the sample to be tested comprises a counter electrode, a mixture of the electrolyte to be tested and electronic conductor fibers, an ion conductor layer a, an ion conductor layer b and a reference electrode which are sequentially arranged from top to bottom. The quantitative evaluation device can solve the problem of small contact area between the counter electrode and the sample to be tested, the problem of side reaction and interference signals generated by direct contact of the sample to be tested with lithium metal, the problem of test interruption caused by lithium dendrite generated by migration of lithium ions onto the lithium foil of the reference electrode, and the problem of incapability of quantitatively analyzing the stability of electrolyte.

Inventors

LI LIFEI
DAI XIN
CHEN XINGLONG

Assignees

蓝固(常州)新能源有限公司

Dates

Publication Date: 20260505
Application Date: 20230710

Claims (9)

1. The quantitative evaluation device for the stability of the lithium ion solid electrolyte is characterized by comprising the following components: the device comprises a press upper hydraulic plate, a press probe, an upper polar column, a sample sleeve, a lower polar column and a press lower hydraulic plate which are sequentially arranged from top to bottom, wherein the upper polar column and the lower polar column are respectively provided with a binding post; a pressure gauge connected to the press probe; Electrochemical workstations respectively connected with the upper post binding post and the lower post binding post; The sample to be tested comprises: The counter electrode, the mixture of the electrolyte to be tested and the electronic conductor fiber, the ion conductor layer a, the ion conductor layer b and the reference electrode are sequentially arranged from top to bottom; the electron conductivity of the electron conductor fiber is more than 10 5 S/cm; The ratio of the surface area of the electrolyte to be tested to the surface area of the electronic conductor fiber is 1 (50-100); The ionic conductivity of the ion conductor layer a is more than 10 -4 S/cm, the electronic conductivity is less than 10 -8 S/cm, the Young modulus is less than 25GPa, and the oxidation-resistant cut-off voltage which can be born is more than or equal to 4.5V; The ionic conductivity of the ion conductor layer b is more than 10 -4 S/cm, the electronic conductivity is less than 10 -8 S/cm, the Young modulus is less than 25GPa, and the reduction-resistant cutoff potential which can be born is less than or equal to 0.6V.
2. The quantitative evaluation device for the stability of a lithium ion solid electrolyte according to claim 1, wherein the counter electrode is made of a material selected from the group consisting of carbon-coated aluminum foil, gold foil, platinum foil, steel foil and carbon-coated steel foil.
3. The quantitative evaluation device for the stability of a lithium ion solid electrolyte according to claim 1, wherein the electrolyte to be measured is a lithium ion conductor.
4. The quantitative assessment device for the stability of a lithium ion solid electrolyte according to claim 1, wherein the electronic conductor fiber is selected from one or more of metal fiber, ke Qinhei, single-walled carbon nanotube, multi-walled carbon nanotube and vapor grown carbon fiber.
5. The quantitative evaluation device for the stability of a lithium ion solid electrolyte according to claim 1, wherein the reference electrode is In x -Li y , wherein x is more than or equal to 5:95 and y is more than or equal to 45:55.
6. The quantitative evaluation method for the stability of the lithium ion solid electrolyte is characterized by comprising the following steps of: The quantitative evaluation device for the stability of the lithium ion solid electrolyte is characterized in that an ion conductor layer b, an ion conductor layer a, a mixture of an electrolyte to be tested and an electronic conductor fiber are sequentially arranged in a sample sleeve, a counter electrode and a reference electrode are respectively arranged on two sides of the mixture of the electronic conductor fiber and the ion conductor layer b for pressing, then an electrochemical workstation is used for testing the electrochemical stability under continuous pressure, and quantitative evaluation for the stability of the lithium ion solid electrolyte is realized by responding to the integral area of current and voltage.
7. The quantitative evaluation method for the stability of a lithium ion solid electrolyte according to claim 6, wherein the process of sequentially arranging the ion conductor layer b, the ion conductor layer a, the mixture of the electrolyte to be tested and the electronic conductor fiber comprises the following steps: firstly, placing components of an ion conductor layer b into a sample sleeve, performing first pressing to form the ion conductor layer b, then placing components of an ion conductor layer a onto the ion conductor layer b in the sample sleeve, performing second pressing to form the ion conductor layer a, and finally placing a mixture of electrolyte to be tested and electronic conductor fibers onto the ion conductor layer a in the sample sleeve, and performing third pressing; the pressure of the first pressing is 50-600 MPa, and the time is 1-5 min; the pressure of the second pressing is 50-600 MPa, and the time is 1-5 min; the pressure of the third pressing is 50-600 MPa, and the time is 1-5 min.
8. The quantitative evaluation method for the stability of the lithium ion solid electrolyte according to claim 6, wherein the pressing pressure is 50-600 mpa and the time is 1-5 min; the value of the continuous pressure is 10-600 MPa.
9. The method for quantitatively evaluating the stability of the lithium ion solid electrolyte according to claim 6, wherein in the process of testing the electrochemical stability, a cyclic test method of step lifting, constant voltage stabilization, step lifting and constant voltage stabilization is adopted for voltage lifting, and the step lifting, constant voltage stabilization, step lifting and constant voltage stabilization is specifically carried out by lifting to a second-stage voltage U 2 ,U 2 =U 1 +DeltaU under an initial voltage U 1 for a constant time t and lifting to a third-stage voltage U 3 ,U 3 =U 2 +DeltaU under a voltage U 2 for a constant time t until the voltage reaches a cut-off voltage U n =U Cut-off –U 0 to be tested.

Description

Quantitative evaluation device and method for stability of lithium ion solid electrolyte Technical Field The invention relates to the technical field of lithium ion solid-state batteries, in particular to a quantitative evaluation device and method for stability of lithium ion solid-state electrolyte. Background The lithium ion solid electrolyte is a core material of the lithium ion solid battery, and meanwhile, an electrochemical window (electrochemical stability) of the solid electrolyte is a key index of the solid electrolyte. The electrochemical stability of a solid-state electrolyte determines the voltage range over which it can be used and ultimately affects the positive and negative electrode materials used in conjunction therewith, and thus ultimately the electrochemical system of the overall battery. At present, the evaluation method disclosed in the prior art mainly comprises the following steps: 1. Assembled battery test: One of the current methods for characterizing electrochemical stability of solid electrolyte is to mix the solid electrolyte with a positive electrode or negative electrode material, assemble the solid electrolyte into a battery, and determine whether the solid electrolyte can withstand a voltage range during charging and discharging of the battery by testing ICE (first charge and discharge efficiency), CE (coulombic efficiency) and cyclic capacity retention rate of the whole battery during charging and discharging. However, the method has the following defects that after the solid electrolyte is mixed with the anode material and the cathode material, a charge-discharge test is carried out, so that the system becomes complex, the stable voltage range of the electrolyte cannot be judged directly, the interface of the electrolyte/the active material is increased, the intrinsic stable signal of the electrolyte can be covered by side reaction at the interface, the test time of the method is long, the ICE data can be obtained after 20 hours of the first cycle at 0.1C, and the subsequent long-cycle test is longer than a few months, so that the large-flux screening of the solid electrolyte material is not facilitated. 2. Electrolyte stability was tested using CV (volt-ampere cycle): The electrolyte to be tested is assembled into the structure shown in fig. 1 for testing, wherein (1) -a counter electrode adopts an electronic conductor and an ion blocking electrode and is kept stable in a test voltage range, and is generally stainless steel, and (2) the sample to be tested is a solid electrolyte powder material to be tested, which is pressed into a sheet shape in a die, and (3) -a reference electrode plays a role of providing a reference voltage, is required to be an electronic conductor, can keep the potential of the reference electrode unchanged in the test range and does not change along with the embedding of lithium ions, and generally uses a lithium foil as the reference electrode. After the electrolyte material to be tested is assembled according to the above method, the above structure is tested, typically using an electrochemical workstation, in particular, using a CV method, i.e. applying a continuously and steadily increasing voltage to the counter electrode, for example, increasing the voltage from 2.5V to 4.5V at an increasing rate of 5mV/S, and recording the change of current in the process. However, the method has the following defects that (1) the decomposition of the solid electrolyte under different voltages mainly occurs at the interface contacted with the electronic conductor, so in the method, the decomposition of the solid electrolyte only occurs at the contact interface of the counter electrode and the sample to be detected, and the contact area at the interface is a two-dimensional plane, so the contact area is smaller, and the electric signal generated by the decomposition of the solid electrolyte is smaller and is not easy to capture. (2) The sample to be measured is directly contacted with the lithium foil serving as the reference electrode, however, most of solid electrolytes are thermodynamically unstable (partial oxide electrolytes, almost all sulfide electrolytes and halide electrolytes) to lithium metal due to the low potential (0V Vs. Li) and extremely active chemical property of the lithium metal, so that side reactions generated at the interface between the reference electrode and the sample to be measured can generate interference electric signals, and the test signals are fluctuated and unstable, so that judgment is inaccurate. (3) On the other hand, because of lower potential of lithium, lithium dendrite is very easy to be generated by the deposition of lithium ions directly on the lithium foil, and after the lithium dendrite grows and pierces the sample to be tested, electrons between the reference electrode and the counter electrode are conducted, so that the potential difference between the two electrodes is zero, and the sample cannot be tested. (