阅读说明：本技术 一种用于电化学反应测试的模型电池和测试方法 (Model battery for electrochemical reaction test and test method ) 是由 余慧杰 李大伟 刘兴宇 李江涛 马明明 于 2020-12-11 设计创作，主要内容包括：本发明公开了一种用于电化学反应测试的模型电池,其特征在于,包括石英外壳,夹具,石英外壳上盖板,悬臂梁结构电极,CCD相机,对电极,电池测试仪,所述悬臂梁结构电极为双层悬臂梁结构,包括活性层与集流体层,所述悬臂梁结构电极外覆盖有隔膜、两端设有极耳连接对电极,由夹具将悬臂梁结构电极、隔膜和对电极夹紧,并固定在石英外壳的内壁上,进行充放电循环,CCD相机用于原位记录该模型电池随锂离子浓度和结构变化引起的变形并保存在计算机中,由电池测试仪结合力学模型用来分析变形过程中曲率与材料参数、杨氏模量和充电状态之间的关系。(The invention discloses a model battery for electrochemical reaction testing, which is characterized by comprising a quartz shell, a clamp, a quartz shell upper cover plate, a cantilever beam structure electrode, a CCD (charge coupled device) camera, a counter electrode and a battery tester, wherein the cantilever beam structure electrode is of a double-layer cantilever beam structure and comprises an active layer and a current collector layer, a diaphragm covers the cantilever beam structure electrode, two ends of the cantilever beam structure electrode are provided with tabs for connecting the counter electrode, the cantilever beam structure electrode, the diaphragm and the counter electrode are clamped by the clamp and fixed on the inner wall of the quartz shell for charge-discharge circulation, the CCD camera is used for recording the deformation of the model battery caused by the lithium ion concentration and structure change in situ and storing the deformation in a computer, and the battery tester is combined with a mechanical model for analyzing the relationship among the curvature, the material parameter, the Young modulus and the charging state in the deformation process.)

1. A model battery for electrochemical reaction testing is characterized by comprising a quartz shell, a clamp, a quartz shell upper cover plate, a cantilever beam structure electrode, a CCD (charge coupled device) camera, a corresponding electrode and a battery tester, wherein the cantilever beam structure electrode is of a double-layer cantilever beam structure and comprises an active layer and a current collector layer, a diaphragm covers the cantilever beam structure electrode, tabs are arranged at two ends of the cantilever beam structure electrode and connected with the corresponding electrode, the cantilever beam structure electrode, the diaphragm and the corresponding electrode are clamped by the clamp and fixed on the inner wall of the quartz shell for charge and discharge circulation, the CCD camera is used for recording deformation of the model battery caused by lithium ion concentration and structure change in situ and storing the deformation in a computer, and the battery tester is combined with a mechanical model and used for analyzing the relation among curvature, material parameters, Young modulus and charging state in the deformation process.

2. The model cell for electrochemical reaction testing as recited in claim 1, wherein the quartz casing and the cover plate of the model cell are made of quartz for preventing corrosion of the electrolyte and influence thereof from an external environment.

3. The model cell for electrochemical reaction testing of claim 1, wherein the holder is made of stainless steel to facilitate the fixation and testing of the cantilever-structured electrode.

4. The model battery for electrochemical reaction test as claimed in claim 1, wherein the in-situ recording controls the deformation of the controller in real time by controlling the intercalation amount of lithium ions, thereby implementing the trapping function.

5. The model cell for electrochemical reaction testing of claim 1 wherein the ratio of the thickness of the active layer to the current collector layer in the cantilever electrode is varied and the relationship between the progress of bending deformation and the electrode structure parameters is recorded.

6. The model cell for electrochemical reaction testing of claim 1, wherein the curvature and changes in material parameters, structural parameters, and lithium ion concentration during electrode deformation are accounted for in conjunction with a physical model.

7. A test method for electrochemical reaction test, in particular to a test method for an electrochemically controlled large-deformation high-strength controller, which adopts the cantilever beam structure electrode test system as claimed in claim 1 to operate, and is characterized in that the operation steps are as follows:

1) assembled electrochemical controller reaction environment

2) Structural design of cantilever beam electrode

3) Charge and discharge cycling of cantilever beam electrode

4) Collecting image by image collecting program, and recording electrode plate section deformation in situ

5) And analyzing the relation between the curvature and material parameters, Young modulus and charging state in the deformation process by using the developed mechanical model.

Technical Field

The invention relates to a model battery for electrochemical reaction test and a test method, which can realize controllable super bending deformation by designing a lithium battery electrode structure and adjusting electrochemical reaction time, are expected to be used as a controller under special chemical reaction conditions, and belong to the technical field of electrochemical controllers.

Background

Controllers are a very important class of devices. There are many mechanisms of action to achieve control, such as: electrical, magnetic, thermal, optical, and the like. However, it is still a hot spot of current research to realize accurate and effective control in the control process. Lithium battery active materials, due to their controlled volumetric deformation and relatively high strength of the electrodes, promise for the use of such materials to prepare controllers in electrochemical environments, and for applications in certain complex environments and to perform certain mechanical functions.

Currently, a variety of electrochemically active materials are used for electrochemically controlled controllers. Among them, active materials such as carbon nanotubes and graphene have drawn much attention due to their remarkable electro-mechanical energy conversion properties. Fraysse et al fixes two pieces of single-walled carbon on a tape to prepare a micro cantilever beam which can work in a low-voltage environment. Liu et al used graphene materials to make a controller that can respond differently mechanically to chemical reactions. In recent years, the development of various lithium battery electrode active materials provides a new idea for designing a controller with better performance. For example, graphite can achieve a volume expansion of 10% and silicon up to 400%. The coating prepared by the active material can expand and contract in the electrochemical reaction process, and deformation mismatch can be generated at the interface under the constraint of a current collector. This mismatch in deformation in turn causes significant bending deformation of the electrode. This type of layered electrode is a common controller structure that can be used to capture objects or perform control functions. Laura Valero Conzuelo et al found that conducting polymers can undergo a oscillatory process by ion-exchanging with electrolytes. L. valero et al found that the layered structure (PPy-DBS-ClO 4/tape) can be controlled in its deformation by varying the magnitude of the current. Pei et al indicate that this beam bending process is an effective means to measure the volume change, mass transport, and phase relaxation that occurs during electrochemical cycling. Meanwhile, a relevant model is established to analyze the direct relationship between the bending and the Young modulus, the thickness change and the volume change. Christophersen et al further extend the theoretical model by considering the gradient of strain and modulus in the thickness direction. Du et al developed a multi-layer bending model to analyze the bending deformation behavior of the beam. However, there is still a lack of an effective controlled bending deformation of sufficient strength to perform the control function in a specific electrochemical environment.

Disclosure of Invention

The technical problem to be solved by the invention is how to use the lithium battery active material to prepare the controller in an electrochemical environment, and to apply the controller in some specific complex environments and realize certain mechanical functions.

In order to solve the above technical problems, the present invention provides a model battery for electrochemical reaction testing, it is characterized by comprising a quartz shell, a clamp, an upper cover plate of the quartz shell, a cantilever beam structure electrode and a CCD camera, a corresponding electrode and a battery tester, wherein the cantilever structure electrode is a double-layer cantilever structure and comprises an active layer and a current collector layer, the two ends of the cantilever beam structure electrode are provided with tabs to connect with corresponding electrodes, the cantilever beam structure electrode, the diaphragm and the corresponding electrodes are clamped tightly by a clamp, and fixed on the inner wall of the quartz shell for charge-discharge circulation, the CCD camera is used for in-situ recording the deformation of the model battery caused by the lithium ion concentration and structural change and storing in a computer, the battery tester is combined with a mechanical model to analyze the relation between the curvature and the material parameters, Young modulus and charging state in the deformation process.

The quartz shell and the cover plate of the model battery are made of quartz and used for avoiding the corrosion of electrolyte and the influence of external environment on the electrolyte.

The fixture is made of stainless steel, and facilitates fixing and testing of the cantilever beam structure electrode.

Wherein, the in-situ recording controls the deformation of the controller in real time by controlling the embedding amount of the lithium ions, thereby realizing the capturing function.

Preferably, the thickness ratio of the active layer to the current collector layer in the cantilever electrode is changed, and the relation between the bending deformation process and the structural parameters of the electrode is recorded.

Preferably, the change of the curvature and the material parameter, the structural parameter and the lithium ion concentration in the electrode deformation process are described by combining a physical model.

A test method for electrochemical reaction test, in particular to a test method for an electrochemically controlled large-deformation high-strength controller, which adopts the cantilever beam structure electrode test system as claimed in claim 1 to operate, and is characterized in that the operation steps are as follows:

1) assembled electrochemical controller reaction environment

2) Structural design of cantilever beam electrode

3) Charge and discharge cycling of cantilever beam electrode

4) Collecting image by image collecting program, and recording electrode plate section deformation in situ

5) And analyzing the relation between the curvature and material parameters, Young modulus and charging state in the deformation process by using the developed mechanical model.

Drawings

Fig. 1 is a schematic diagram of a testing apparatus for a controller according to the present invention, wherein 1a is a schematic diagram of a quartz casing and 1b is a schematic diagram of a cover plate;

FIG. 2 is a schematic diagram of a model cell and in-situ observation system according to the present invention;

FIG. 3 is a schematic diagram of the deformation of the controller during an electrochemical cycle;

FIG. 4 is a graph of the effect of different materials and structural parameters on bending deformation, 4a state of charge, 4b Young's modulus ratio of current collector to active, 4c thickness ratio of active layer to current collector;

fig. 5 is a graph of the controller bending deformation, the evolution rule of voltage and curvature along with the charging and discharging states and the thickness ratio, 5a, b are graphs of the bending deformation of the graphite composite electrode in the charging process, 5c are evolution processes of different electrode voltages along with time, and 5d are evolution processes of electrode curvatures along with time in different thickness ratios;

FIG. 6 shows the bending deformation of the graphite composite electrode in the same charging state;

FIG. 7 is a direct comparison of the results of the controller bending deformation experiments with the physical model.

Detailed Description

In order to make the invention more comprehensible, preferred embodiments are described in detail below with reference to the accompanying drawings.

Examples

The invention provides a new controller design idea, and simultaneously, the deformation process of the controller is analyzed by combining a theoretical model, so that guidance is provided for designing a high-strength and large-deformation controller. In the experiment, the reaction environment is a closed space full of electrolyte environment, and the external device is completely made of quartz, so that the influence of additional reaction on the test result is avoided. The bending deformation during the electrochemical cycle is recorded by combining a CCD camera in the reaction process, and meanwhile, the bending curvature of the GETDATA extraction electrode is combined.

By adjusting the reaction time, the intercalation amount of lithium ions, namely the expansion deformation of the reaction layer, is controlled, and further the deformation degree of the reaction electrode is controlled. Through the structural design of the counter electrode, the thickness ratio of the electrode active layer to the current collector is mainly adjusted, and other parameters are kept consistent. Meanwhile, the relation between the electrode structure size and the bending curvature in the electrode deformation process is analyzed by combining a physical model, and theoretical guidance is provided for the controllable deformation controlled by electrochemistry.

The electrochemical controller with higher strength has the structural characteristics that:

a novel model battery is designed. The model battery shell used in the reaction is completely prepared by combining quartz and stainless steel, thereby avoiding the corrosion influence of electrolyte on the battery shell and ensuring the pureness of the reaction environment.

The test electrode in the experiment is a double-layer cantilever beam structure, comprises an active layer and a metal current collector and is fixed in the model shell. And simultaneously, a CCD camera is used for recording the deformation of the electrode pole piece in situ in the electrochemical circulation process. In combination with the image acquisition procedure, a longer acquisition process can be performed in the glove box.

And a mechanical model is combined for analyzing the relation between the curvature and material parameters, Young modulus and charging state in the deformation process.

The electrochemical controller of the present invention is characterized in that:

a novel reaction device is designed, the device is completely made of quartz materials, and the influence of other impurities on the reaction environment is eliminated, as shown in figure 1. Meanwhile, the window made of quartz allows the deformation process of the electrode to be directly recorded, and the working process of the controller can be conveniently observed in real time.

And accurately giving the evolution process of the electrochemical controller along with the charge-discharge state, and simultaneously giving the relation between the evolution process and the structural size change.

And analyzing the relation between the curvature and material parameters, the material performance, the structure parameters and the charging state in the deformation process by combining a mechanical model. To explain the phenomenon obtained in the experiment, a double-layer beam model shown in fig. 2 was established. The model mainly comprises a layer of graphite electrode and a layer of current collector. Wherein h is₁And h_cThe thicknesses of the active layer and the current collector are indicated, respectively. Lithium ions are inserted into and extracted from the active layer through the outer side of the active layer, so that expansion and contraction of the active layer are caused, and meanwhile, the lithium ions are restrained by the current collector, and compressive stress is generated at the interface. This mismatch in deformation can cause bending of the entire electrode as shown in fig. 3.

The thickness direction is defined as the z-axis, and the in-plane directions are the x-axis and the y-axis. Based on the theory of small deformation, the relationship between the curvature and the deformation parameter of the material can be obtained as follows:

here, the number of the first and second electrodes,

rearranging the formula 1 to obtain a relational expression between the curvature kappa and the electrode material parameters:

here, R_h＝h₁/h_cAnd R_E＝E_c/E₁The thickness ratio and modulus ratio of the electrode active layer to the current collector are respectively expressed, Ω represents partial molar volume, and c represents lithium ion concentration. As can be seen from the above formula, the change in the dimensionless curvature is mainly affected by the lithium ion intercalation amount, the thickness ratio, and the modulus ratio.

Compared with the prior art, the invention has the beneficial effects that:

designing a controller for an electrochemical reaction using an active material of a lithium battery;

the deformation of the controller is controlled in real time by controlling the charging and discharging states;

the deformation of the controller is controlled by selecting the material type and designing the structure;

through the design of the thickness ratio of the electrode, the relation between the bending deformation of the electrode and the structural parameters of the active layer is found, and guidance is provided for the design of a controller.

As shown in fig. 1 and 2, an environment for electrochemical reactions is provided according to an embodiment of the invention. The device comprises a model battery shell, an electrode cantilever beam and a CCD camera. In the test process, the reaction cantilever can be placed in a reaction environment for cyclic test and the deformation process is recorded.

The theoretical model for the controller bending deformation process caused during the electrode reaction process is shown in fig. 3. In conjunction with equation one, it can be seen that: the state of charge, the young's modulus ratio, and the thickness ratio all affect the bending deformation of the controller. As can be seen from fig. 4, the bending curvature gradually increases linearly with increasing state of charge; with the decrease of the Young modulus of the active layer, the bending curvature has the change trend of increasing firstly and then decreasing; the bending curvature also has a tendency to increase first and then decrease as the thickness of the active layer increases. Therefore, the controller can realize accurate control of bending deformation by selecting different charging states, different active layers and current collector materials and different thickness ratios.

The following test examples discuss the effect of thickness ratio on bending curvature. In the test process, the reaction electrode is mainly prepared from MCMB particles, binders SBR and CMC in a mass ratio of: 90: 7.5: 2.5. wherein deionized water is used as a solvent to dissolve the binder. After the copper foil is completely dissolved, the conductive agent and the active material are sequentially added according to the proportion, stirred uniformly to form slurry, and then coated on a current collector (copper foil, the thickness of which is 35 microns and 9 microns respectively). After complete drying, the electrode was pressed down to 70% of the original electrode thickness by means of a roller press (MTI Corp, shenzhen). In addition, LiFePO4 is selected as the anode material to meet the lithium ion supply.

The rolled MCMB graphite electrode was measured for overall thickness by a thickness meter (Mitutobo). By analysis, the thickness ratios of the active layer to the current collector were found to be 5.7, 7, 8, 10.1, 16.7, and 26.2, respectively. During the bending deformation, the deformation graph is shown in fig. 5 and 6.

TABLE 1 thickness ratio of different electrodesAnd theoretical capacity

During constant current charging, the capacity of the electrode is determined by equation cFV ═ It. Where c is the concentration of lithium ions, F is the Faraday constant, V is the volume of the active material, I is the current density, and t is the charge time. Then the theoretical capacity is mc_mWhere c is_m345mAh/g is the specific capacity of the active material, and m is the mass of the active material. The battery is charged and discharged at constant current under the charging rate of 0.1C (fully charged in 10 hours), and the voltage range is 2.0-4.2V.The relatively small charge rate is adopted here to ensure the uniform distribution of lithium ions, so that the concentration gradient in the thickness direction can be omitted in the theoretical calculation. The frequency of data acquisition in the electrochemical cycling experiments was set to 1 Hz. The camera takes one picture every 1 minute. The state of charge SOC is selected to be 40% and the time corresponding to the lithium insertion phase is 240 minutes.

The curvature data corresponding to the experimental output, and the physical model, where Ω is 3.56 × 10^-6m³The molar volume is expressed as mol,/mol, c is 26400mol/m3 represents the lithium ion concentration, the young modulus of the copper foil of the current collector is 117GPa, and the young modulus of the active layer of the composite electrode MCMB is 148MPa,175MPa and 173MPa respectively corresponding to different states of charge (SOC 20%, SOC 30%, SOC 40%). The fitting result is shown in fig. 7, and the result shows that the theoretical model is perfectly fitted with the experimental result. Therefore, the method can provide a new design method for designing a high-strength and large-deformation controller.