KR101499353B1 - Binder for anode in lithium ion battery, anode in lithium ion battery comprising the same, lithium ion battery comprising the same, and manufacturing method for the same - Google Patents

Abstract

In the present invention, provided is a binder for an anode in lithium ion batteries having a β-cyclodextrin polymer which is a hyperbranched net structure. Specifically, provided is the binder having the hyperbranched polymer net structure, which is originated from polymerization of a unique and large-sized structure of β-cyclodextrin (β-CD) and a three-dimensional structure of the unit β-cyclodextrin (β-CD). The binder facilitates interaction of Si-binder and self-healing ability and has an outstanding effect of improving mechanical stability on the film of electrodes, and can resolve chronic irregular cycle life of anode in Si.

Description

TECHNICAL FIELD The present invention relates to a binder for a lithium ion battery anode, a lithium ion battery negative electrode including the same, a lithium ion battery including the same, and a method of manufacturing the lithium ion battery. for the same}

The present invention relates to a lithium ion battery negative electrode binder, a lithium ion battery negative electrode comprising the same, a lithium ion battery, and a method of preparing the same. More particularly, the present invention relates to a unique macrocyclic structure of? -Cyclodextrin (? The present invention relates to a binder for a lithium ion battery negative electrode having a hyperbranched polymer network structure originating from the polymerization of a unit? -Cyclodextrin into a three-dimensional structure, a lithium ion battery negative electrode comprising the same, a lithium ion battery and a method for producing the same.

Many battery companies are paying a great deal of attention to silicon (Si) as a lithium-ion battery (LIB) anode material due to their excellent theoretical gravimetric capacity (~ 4200 mAh g ^-1 ). The theoretical mass capacity of silicon, (370 mAh g < ^-1 >).

The high mass capacity of Si is expected to play an important role in the realization of many key lithium-ion battery (LIB) objectives. Good examples from this point of view are improved portable electronic devices that require high power consumption and electric vehicles that have a long drive distance for each charge.

Despite the advantageous mass capacity, Si is a disadvantage of a short cycle life originating from a large volume change during repeated Li (de) insertion. In lithiation to form a Li _4.4 Si alloy, Si undergoes ~ 300% volume expansion compared to its initial state.

A significant volume change of Si during battery operation triggers deadly deterioration mechanisms such as crushing of the active material, loose contact between the Si and the carbon conductive material, film separation from the current collector, and formation of a destabilized solid-electrolyte interface (SEI) .

Various electrode designs, including nanostructured Si, have been shown to be effective in mitigating such deterioration mechanisms, but now the choice of binder also has a significant impact on cell performance.

It has been proposed that the ideal binder for the Si electrode retains effective interactions with the native oxide silicon layer on the Si surface as well as the solid polymer backbone and copper (Cu) oxides on the Cu current collector.

In particular, focusing on the latter aspect, compared with conventional poly (vinylidene fluoride) (PVDF), which acts primarily on Van der Waals interactions, a polymeric binder containing carboxylic acid and / Recent research has shown that hydrogen bonding interaction with Si active material can be utilized to achieve excellent cycling performance.

Representative binders with hydrogen bonding capabilities include carboxymethylcellulose (CMC), polyacrylic acid (PAA), and alginate (Alg).

Among these series of binders, the number of carboxylate sites per given molecular weight of the polymer directly affects the interaction with Si and hence the cycle life.

Although the improved cycle life based on these polymeric binders has made considerable progress in the Si anode studies, the one-dimensional (1D) linear backbone of these polymers limits the interaction with Si to only point or line contact. It is therefore highly desirable to develop a new polymeric binder that can act beyond this interaction

Accordingly, a problem to be solved by the present invention is to provide a binder for a cathode of a lithium secondary battery having a multidimensional structure that can expand the interaction with Si and an application method thereof.

In order to solve the above problems, there is provided a binder for a lithium ion battery anode comprising a cyclodextrin polymer having a hyperbranched network structure.

In one embodiment of the present invention, the cyclodextrin polymer is any one selected from the group consisting of alpha (alpha), beta (beta) and gamma (gamma) cyclodextrins.

 In one embodiment of the invention, the cyclodextrin polymer is a? -Cyclodextrin polymer of the structure:

Wherein n is an integer of 10 to 10000 and R is a compound of any one of the following formulas

In one embodiment of the present invention, the? -Cyclodextrin polymer is prepared by reacting a? -Cyclodextrin monomer with epichlorohydrin, and the hydroxyl group of the? -Cyclodextrin monomer and the ether of epichlorohydrin Group is combined, whereby the? -Cyclodextrin polymer is polymerized

In one embodiment of the present invention, the lithium ion battery negative electrode binder further comprises alginate, and the alginate is 10 to 15% by weight of the binder.

The present invention also provides a lithium ion battery negative electrode comprising a binder for a lithium ion battery negative electrode.

In one embodiment of the present invention, the lithium ion battery negative electrode contains silicon as the negative electrode active material.

In one embodiment of the present invention, the binder for a lithium ion battery anode comprises a? -Cyclodextrin polymer having a hyperbranched network structure, and the? -Cyclodextrin polymer of the hyperbranched network structure is a mixture of the silicon and the hydrogen And the like.

In one embodiment of the present invention, the silicon is hydrogen bonded at a plurality of positions with the binder for the lithium ion battery negative electrode, and the binder for the lithium ion battery negative electrode is selected from the group consisting of a hyperbranched network structure? -Cyclodextrin polymer and alginate .

In one embodiment of the present invention, the agglomeration of the? -Cyclodextrin polymer of the hyperbranched network structure by the alginate is reduced, and the electrostatic repulsion between the alginates is reduced by the? -Cyclodextrin polymer do.

The present invention also provides a lithium ion battery including the above-described lithium ion battery negative electrode.

The present invention provides a binder of a hyperbranched polymer network structure originating from the polymerization of a unique macrocyclic structure of? -Cyclodextrin (? -CD) and a three-dimensional structure of the unit? -Cyclodextrin. The binder according to the present invention facilitates the self-healing ability as well as the improved Si-binder interactions, achieves a considerable effect in improving the mechanical stability of the electrode film, and can solve the chronic insufficient cycle life of the Si negative electrode have.

Fig. 1 (a) is an alginate (Alg), and Fig. 1 (b) is a structural formula and a diagram of a β-cyclodextrin polymer (β-CDp) binder.
Figure 1c is a schematic view Si- binder for the lithiated / de-lithiated (c) Si _Alg for the Si (sphere), Fig. 1d is a schematic diagram of the structure of the binder Si- Si _β-CDp.
Figure 2a is the result of a comparison of the amount of binder in the Si / binder blend calculated based on TGA analysis before and after washing the blend with water, and Figure 2b is the bulk scale stripping characterization analysis for the Si / binder film based on two binders .
Figure 3a is _{β-Si CDp,} Si _β-CD, and the first voltage profile, sapdo of Si _Alg is a result showing the initial coulombic efficiency (ICE) for each respective sample.
FIG. 3B is a cycle performance graph of Si _{? -CDp} and Si _{? -CD} measured at 1C (4200 mA g ^-1 ).
Figure 3c is a 1D-based electrode binder _{(β-Si CDp, CMC} Si, and Si _Alg), a cycle of the _{β-Si CDp} binder used in the electrode according to the present invention, which is commonly used as measured at 1C (4200 mA g ^-1) Performance comparison result.
Figure 3d is a cyclic performance result of Si electrodes based on a hybrid binder approach using different ratios of beta -cyclodextrin polymer (beta -CDp) and alginate (Alg).
FIG. 4A is a graph showing the aggregation characteristics of β-cyclodextrin polymer (β-CDp) due to intramolecular hydrogen bonding, FIG. 4B is an elongated feature of Alg due to electrostatic repulsion between carboxylates, FIG. Fig.
Figure 5 is a SEM image of a _β-Si and Si _{CDp Alg} at different steps during one complete cycle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the width, length, thickness, etc. of components may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

The present invention provides a binder having a structure that increases the number of contacts between Si and the binder for further improvement in cycle life.

Based on this motivation, we provide a hyperbranched cyclodextrin polymer (CDp) as a binder for a new silicon-based anode. In the present invention, the term " hyperbranched structure "refers to a structure in which the main chain is connected to at least one branch by a plurality of branches and has a net-like shape as a whole. Further, the cyclodextrins include alpha (alpha) type consisting of six sugar molecules and gamma (gamma) type cyclohexane type group consisting of eight sugar molecules in addition to beta -cyclodextrin polymer (beta -CDp) Since dextrin is also a structure capable of forming at least two hydrogen bonds with a silicon anode active material, this also falls within the scope of the present invention.

The present invention uses a network structure polymer capable of hydrogen bonding with an anode active material such as silicon, and maintains a stable Si-binder bond even in the expansion-contraction process of Si.

The structural formula of the binder according to one embodiment of the present invention is shown in the following chemical formula 1.

[Chemical Formula 1]

Wherein n is an integer of 10 to 10000, and R is any one of the following formulas.

As can be seen from the above formula (1),? -Cyclodextrin is a 7-membered pericyclic ring in which glucose is incorporated as a monomer unit, and? -Cyclodextrin polymer is a form in which such 7-membered pericyclic ring is connected.

In one embodiment of the present invention, the use of the beta -cyclodextrin polymer as a binder is industrially meaningful because beta -cyclodextrin can be easily synthesized from starches by enzymatic processes.

The presence of primary and secondary alcohols makes [beta] -cyclodextrin an ideal backbone for further functionalization with epichlorohydrin (EPI), thereby providing a hyperbranched Beta -cyclodextrin is formed.

Fig. 1 (a) is an alginate (Alg), and Fig. 1 (b) is a structural formula and a diagram of a β-cyclodextrin polymer (β-CDp) binder.

Referring to Figures 1A and 1B, the beta -cyclodextrin polymer side chain according to the present invention may be a dihydroxypropyl moiety in the monomeric or dimeric or trimer form, and the bridges may be glyceryl moieties in each form .

Also, Figure 1c is a schematic view Si- binder for the lithiated / de-lithiated (c) Si _Alg for the Si (sphere), Fig. 1d is a schematic diagram of the structure of the binder Si- Si _β-CDp.

Referring to the figure, unlike conventional one-dimensional (1D) polymeric binders, the branched form of the β-cyclodextrin according to the invention exhibits a large number of non-shared interactions at the localized sites of Si. In addition, at the same time, the interconnected hyperbranched network structure of the binder polymer according to the present invention forms a stable electrode film, which leads to remarkable improvement in both the battery capacity and the battery cycle life.

The present invention also demonstrates the effectiveness of a hybrid binder wherein the addition of an optimal amount of 1D Alg binder results in a reduced aggregation of the beta -cyclodextrin polymer (beta -CDP) due to a series of non-covalent interactions, Due to the more uniform distribution, the electrochemical performance of a lithium ion battery using the binder according to the present invention for a negative electrode is further improved.

The? -Cyclodextrin polymer (? -CDp) according to the present invention can be obtained by reacting? -Cyclodextrin with EPI under strongly basic conditions.

The hyperbranched β-cyclodextrin polymer (β-CDp) is composed of β-cyclodextrin monomers containing various hydroxyl groups in the side chain, and because of the indiscriminate reaction of EPI with the hydroxyl groups of β-cyclodextrin Various types of branch structures are formed.

As a result, depending on the polymerization process, a network structure can be obtained in which a unique branch structure of the hyper branched bis-cyclodextrin polymer, in which a series of hydroxyl and ether groups are combined, is connected. As a result, the? -Cyclodextrin polymer is capable of producing multidimensional contacts with Si particles as a binder, so as to counter the volume expansion of Si as compared to conventional linear binders, whereby the manufacture of a negative electrode of excellent mechanical strength It is possible.

In addition, the hydrogen bonding interaction between the hyperbranched polymer network structure and the Si particles can create a self-healing effect on the Si particles that lost initial contact, thereby contributing to the improved cyclability of the electrode .

Furthermore, the? -Cyclodextrin polymer is insoluble in carbonate-based electrolyte solvents, which supports stable properties in the most commonly used LIB electrolytes.

From a structural point of view, the bonding mechanism of the Si electrode with Alg and the beta -cyclodextrin polymer (beta -CDp) is expected to be different, which is referred to in Figures 1c and d.

Referring to FIGS. 1C and 1D above, during Li insertion, Algin strands are forcibly elongated or moved relative to the initial state by the expanded Si particles. Up to this point, Si-Alg interaction can be maintained. At the same cycle, upon delithiation, the Si particles shrink again to their original state, but the Alg binder can not sufficiently follow the shrinkage of Si, resulting in a contact loss between the two components. This problem becomes even more pronounced over extended cycling.

The β-cyclodextrin polymer (β-CDp) according to the present invention, on the other hand, is obtained by reacting a hyperbranched main backbone of β-cyclodextrin polymer (β-CDp) with side groups bonded to the main backbone physically entangled Polymer network structure, which enhances bonding forces with Si particles through pure non-covalent interactions, such as hydrogen bonding and van der Waals forces. Thus, in this polymer network structure, the beta -cyclodextrin polymer (beta -CDp) binder provides multidimensional non-sharing interactions with the Si surface through convoluted side groups (see FIG. 1d).

These interactions not only allow the beta -cyclodextrin polymer (beta -CDp) binder to accommodate the very large volume expansion of Si during the lithiation process, but also maintain Si-binder interactions during delithiation. That is, the Si particles that have lost contact with the binder at certain times of the de-lithiation and subsequent cycles can recover their interaction at other points in the hyperbranched binder network structure, thereby allowing the self- Can play a role throughout, which leads to excellent cycling performance.

Figure 2a is the result of a comparison of the amount of binder in the Si / binder blend calculated based on TGA analysis before and after washing the blend with water, and Figure 2b is the bulk scale stripping characterization analysis for the Si / binder film based on two binders .

2A and 2B, in the case of the β-cyclodextrin polymer (β-CDp) according to the present invention on the Si surface and Alg, which is a binder according to the prior art, the loss effect of Alg binder after washing was very large, This reflects weaker interactions of Alg and Si, which are prior art binders.

That is, referring to the above results, it can be seen that the Si / β-cyclodextrin polymer (β-CDp) and the Si / Algin (Alg) blend, after the same washing step in conjunction with thermogravimetric analysis (TGA) 64.2% and 19.9% of the Si-β-cyclodextrin polymer (β-CDp) in the Si / β-cyclodextrin polymer (β-CDp) Lt; RTI ID = 0.0 > Si-binder. ≪ / RTI >

Referring to Figure 2b, the force versus displacement graph (Figure 2b), which is an indication of the adhesion between Si, the binder and the copper foil, showed a distinctive behavior for each binder, the maximum force (denoted by *) being Si / 2.beta.-cyclodextrin polymer (.beta.-CDp) and Si / alginate (Alg) film were measured to be 2.00 N and 1.72 N, respectively.

In addition, the average force (1.73 N) needed to peel the Si /? -Cyclodextrin polymer (? -CDp) film was significantly higher than the Si / Alg film (1.01 N) of the comparative example.

These values indicate that utilization of the multidimensional hydrogen bonding interaction in the hyperbranched polymer network structure according to the present invention as compared to the Si / Alg film results in higher (higher) Si /? -Cyclodextrin polymer (? -CDp) Providing additional robust evidence of mechanical stability.

In addition, the Si / Alg film is exposed to a considerably large portion of Cu on the uppermost surface of the electrode after the peeling test as compared with the Si /? -Cyclodextrin polymer (? -CDp) It can be concluded that it is an obstacle to the overall mechanical stability of the membrane. On the other hand, the Si /? -Cyclodextrin polymer (? -CDp) film had an enhanced adhesion at this interface and most of the electrode film (instead of Cu) was retained on the top surface after the same peel test, It clearly supports that the dextrin polymer ([beta] -CDp) improves the adhesion between the electrode and the Cu current collector with the adhesion force between the Si particles and the binder in the electrode film.

In addition, the binder effect on cell performance was investigated by a series of galvanostatic measurements. For this test, coin-type half-cells were fabricated in which Li metal was incorporated both as a reference electrode and a counter electrode. Lithium hexafluorophosphate is ethylene carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) is dissolved in a co-solvent mixture (3: 2, v / v / v: 5) (1.15M LiPF 6 ) Electrolyte solution. The electrolytic solution also contains 5 wt% of fluoroethylene carbonate (FEC) as an additive.

In a typical test, the cells were cycled from pre-cycle to C / 10 (420 mAg- ¹ ) and then tested at various higher C-rates in subsequent cycles. In this current study, all C-rates were defined based on the ¹ C value (4200 mAg ^-1 ) rather than the actual charge / discharge period. In addition, to clearly illustrate the importance of the hyperbranched network structure, beta -cyclodextrin itself (not polymerized) was also tested as a control binder. The results of the following analysis show that the Si electrodes based on the β-cyclodextrin polymer (β-CDp), β-cyclodextrin (β-CD) and Alg based on the _examples are Si _β-CDp , Si _{β- Alg} , and the method of manufacturing the electrode is as follows.

Si _{? -CDp} , Si _Alg , and Si _CMC , slurries were prepared by mixing Si nanoparticles, binders of each kind, and SuperP in a weight ratio of 60:20:20 in deionized water. For comparison, a slurry for Si _PVDF was prepared by the same procedure using N-methyl-2-pyrrolidone (NMP, Sigma-Aldrich) as a solvent. In order to compare the cycling performance of Si _β-CDp and Si _β-CD , the composition was Si: Binder: SuperP = 40:40:20 (wt%).

All slurries were cast onto copper foil using the Doctor blade technique. Next, the cast film was dried in a vacuum oven at 70 deg. C for 6 hours. The mass loading of Si was 0.3-0.6 mg cm ^-2 , and the value of each case is shown in the drawing.

Figure 3a is _{β-Si CDp,} Si _β-CD, and the first voltage profile, sapdo of Si _Alg is a result showing the initial coulombic efficiency (ICE) for each respective sample. Was measured at C / 10 (420 mAg ^-1 ) within the potential range of 0.01-1.0 V (Li / Li ⁺ band) in FIG.

FIG. 3B is a cycle performance graph of Si _{? -CDp} and Si _{? -CD} measured at 1C (4200 mA g ^-1 ). 3B, the composition of the electrode was Si: binder: SuperP = 40:40:20 (by weight), and the loading amount of Si was 0.3 mg cm ^-2 .

Figure 3c is a 1D-based electrode binder _{(β-Si CDp, CMC} Si, and Si _Alg), a cycle of the _{β-Si CDp} binder used in the electrode according to the present invention, which is commonly used as measured at 1C (4200 mA g ^-1) Performance comparison result.

Figure 3d is a cyclic performance result of Si electrodes based on a hybrid binder approach using different ratios of beta -cyclodextrin polymer (beta -CDp) and alginate (Alg). 3C and D, the electrode composition was Si: binder: SuperP = 60:20:20 (by weight), and the loading amount of Si was 0.6 mg cm ^-2 .

Referring to the above results, the initial constant current profile of the three samples exhibited a characteristic flatness of Si at 0.1 V during lithiation and 0.45 V during delithiation (Fig. 3a), but the initial coulombic efficiency (ICE) are made different from each other, the _{β-Si CDp,} Si _β-CD, and Si _Alg showed respectively 85.9%, 75.6%, and 84.7%.

Compared with the other two electrodes, the excellent ICE of Si _{beta -CDp} using the binder according to the present invention is superior to the first electrode due to the formation of a more stable SEI layer of the hyperbranched polymer network structure of the? -Cyclodextrin polymer (? -CDp) ) Promotes reversibility during lithiation, and the enhanced reversibility is also reflected in the cycle life.

Referring to the results of FIG. 3b, the cycling performance of Si _{? -CDp} and Si _{? -CD} is similar over 200 cycles when both charging and discharging are measured at 1C in each cycle.

However, both specific capacity and cycle life were much better for Si _β-CDp than for Si _β-CD . The specific capacity of Si _β-CDp starts at 2142 _mAg ^-1 in the first cycle, At 1471 mAg ^-1 , which corresponds to a 68.7% capacity retention rate. On the other hand, Si _β-CD not forming a hyperbranched network structure started at a low dose of 1810 mAg ^-1 and after the same number of cycles, the cost amount dropped drastically to 460 mAg ^-1 , Correspondingly, the importance of self-healing ability and hyperbranched polymer network structure for stable cycling is reaffirmed.

Further, unlike the un polymerized? -Cyclodextrin (? -CD), the? -Cyclodextrin polymer (? -CDp) was insoluble in the electrolyte solution. This difference in solubility can play an important role in the differential cycling performance of these two electrodes. The coulombic efficiency (CE) of Si _β-CDp reached 99.6% in the 200th cycle and the average CE in the cycling range of 2-200 was 99.0%.

As shown in Figure 3c, the cycling performance of Si [ _{beta] -CDp} is similar to that of other conventional 1D polymer binders incorporating Alg, CMC, and PVDF (denoted _SiAlg , Si _CMC , and Si _PVDF , respectively) Electrodes were also compared.

The electrodes were all measured at 1 C for charging and discharging over 100 cycles, after 100 cycles, Si _{? -CDp} , Si _Alg , Si _CMC , and Si _PVDF showed capacity retention rates of 54.4%, 33.4%, 45.7%, and 0.7%, respectively.

Referring to the above results, the poor performance of Si _PVDF can be explained by the weak van der Waals interactions between the Si surface and the binder that can not accommodate significant volume changes of Si during lithification / de-lithiation. Among the remaining binders acting on the basis of hydrogen bonding interactions, Siβ-CDp exhibits better cycling performance compared to SiAlg and SiCMC, which has unique multidimensional hydrogen bonding interactions in Siβ-CDp and self- Prove once again the importance.

It is also assumed that the initial capacity damping of Si? -CD is related to the dynamic environment around the Si particles in the early cycling period. That is, during the initial cycle in which the electrodes continue to find a more stable structure, the inherently agglomerated Si particles can be dispersed into smaller secondary particles during Si volume expansion, resulting in an increased number of interactions between Si and the binder. As a result, the Li ion diffusion around the Si particles can be further disturbed by the presence of the binder, thereby reducing the capacity. It is also expected that the initial capacity damping is due to a certain fraction of the Si particles that are permanently lost by once again falling off the aggregate during the volume expansion of Si. However, once this microelectrode structure is stabilized, most of the Si particles are electrochemically activated through the Li ions approaching through the established diffusion path, while at the same time the overall electrode structure and the given capacity are well preserved during continuous cycling. Additional investigation is required for a complete understanding of the initial attenuation.

In an effort to further improve the electrochemical performance of the Si electrode, a hybrid binder approach in which the hyperbranched beta -cyclodextrin polymer (beta -CDp) was mixed with 1D Alg at different weight ratios was investigated (see Figure 3d). Referring to the above results, the Si electrode showed the best cycling performance when the amount of Alg binder was 13 wt%, and the amount of the binder above or below this value resulted in inferior performance. The capacity retention rates of Si electrodes containing 0, 13, and 27 wt% were 54.4%, 70.6%, and 63.7% after 100 cycles, respectively. The presence of an optimal amount of binder may be related to the stereochemistry of the [beta] -cyclodextrin polymer ([beta] -CDp).

Fig. 4 shows the mechanism of the synergistic effect in the beta -cyclodextrin polymer (beta -CDp) / Alg hybrid binder; Fig. 4a is a graph showing the effect of the beta -cyclodextrin polymer (beta -CDp) Fig. 4B is an elongated feature of Alg due to electrostatic repulsion between carboxylates, and Fig. 4C is a schematic diagram showing the structure of a hybrid binder.

As shown in FIG. 4, the effects of cooperating positively promote the more homogeneous polymer network structure of the binder according to the present invention, and furthermore, Na + from the original Alg also creates a 'glue effect' Distribution and stability.

Referring to FIG. 4, in general, a neutral polymer having a pulling interaction site tends to be entangled itself due to strong intramolecular interactions. For this reason, the β-cyclodextrin polymer (β-CDp) was able to form aggregates through intramolecular hydrogen bonding (FIG. 4a), which reduced the interaction with other neighboring polymer chains, thereby increasing the overall mechanical stability of the Si electrode It got worse.

On the other hand, the three-dimensional form of Alg is elongated because the carboxylate (COO-) gives Coulomb repulsion (Fig. 4b), and therefore the combination of these two polymers is advantageous for the addition of Alg to the? -Cyclodextrin polymer , The β-cyclodextrin polymer (β-CDp) reduces the aggregation of β-cyclodextrin polymer (β-CDp), and the manner in which the electrostatic repulsion between the carboxylate units in Alg can be offset 4c), which results in a more uniformly distributed polymer network structure.

In addition, the sodium ion from Alg is coordinated with the oxygen unit of the? -Cyclodextrin polymer (? - CDp), contributing to a better distribution of the hybrid binder. Thus, the optimal point of 13 wt% is that at this point the Alg strand can most effectively inhibit aggregation of the beta -cyclodextrin polymer (beta -CDp) without compromising the advantageous characteristics of the beta -cyclodextrin polymer (beta -CDp) .

The surface morphology of each Si electrode was analyzed using a scanning electron microscope (SEM) to determine the mechanical stability of the electrode film.

Figure 5 is a SEM image of a _β-Si and Si _{CDp Alg} at different steps during one complete cycle.

In Figure 5, the left column is Si _β-CDp and the right column is Si _Alg image a, b) before the electrochemical process, c, d) after complete lithiation, e, f)

Referring to FIG. 5, both Si _β-CDp and Si _{Alg exhibited} a uniform particle distribution in the initial state before cycling (FIGS. 5 a and b), similar SEI formation that filled the void space between Si particles after initial lithiation (Figures 5c and d). However, the difference of these samples was demonstrated after a complete cycle, Si _{◎ CDp} still other hand that preserves the highly uniform particle size distribution (Fig. 5e), Si _Alg is perpetrated clear that the micrometer scale of the crack across the membrane around the area bar (Fig. 5f), indicating that the [beta] -cyclodextrin polymer ([beta] -CDp) is better at preserving the original film morphology utilizing the superior multidimensional binding ability based on the hyperbranched polymer network structure.

As noted above, the present invention utilizes multidimensional hyperbranched beta -cyclodextrin polymers (beta -CDp) as an excellent binder active material for the Si cathode of lithium ion batteries. According to the present invention, the hyperbranched polymer network structure originating from the polymerization of the .beta.-cyclodextrin (.beta.-CD) into the three-dimensional structure of the unit .beta.-cyclodextrin and the unique macroreticular structure of the .beta.- The present invention provides a method for manufacturing a lithium secondary battery comprising the steps of: (a) providing a lithium secondary battery comprising a binder, A cyclodextrin polymer (beta -CDp) binder may be used in combination.

Claims (14)

A binder for a lithium ion battery cathode comprising a cyclodextrin polymer of hyperbranched network structure. The method according to claim 1,
Wherein the cyclodextrin polymer is any one selected from the group consisting of alpha (alpha), beta (beta) and gamma (gamma) cyclodextrins. The binder for a lithium ion battery negative electrode according to claim 2, wherein the cyclodextrin polymer is a? -Cyclodextrin polymer having the following structural formula.

Wherein n is an integer of 10 to 10000 and R is a compound of any one of the following formulas

The method of claim 3,
Wherein the? -Cyclodextrin polymer is prepared by reacting a? -Cyclodextrin monomer with epichlorohydrin. 5. The method of claim 4,
Wherein the? -Cyclodextrin polymer is polymerized by bonding a hydroxyl group of the? -Cyclodextrin monomer with an ether group of epichlorohydrin. The lithium ion battery negative electrode binder according to claim 5,
Wherein the binder further comprises alginate. The method according to claim 6,
Wherein the alginate is 10 to 15% by weight of the binder. A lithium ion battery negative electrode comprising a binder for a lithium ion battery negative electrode according to any one of claims 1 to 7. 9. The method of claim 8,
Wherein the lithium ion battery negative electrode comprises silicon as an active material of the negative electrode. 10. The method of claim 9,
Wherein the binder for the lithium ion battery cathode comprises a? -Cyclodextrin polymer of hyperbranched network structure, and the? -Cyclodextrin polymer of the hyperbranched network structure is hydrogen bonded to the silicon Ion battery cathode. 11. The method of claim 10,
Wherein the silicon is hydrogen bonded at a plurality of positions with the binder for the lithium ion battery negative electrode. 12. The method of claim 11,
Wherein the binder for the lithium ion battery cathode further comprises a? -Cyclodextrin polymer and a alginate in a hyperbranched network structure. 13. The method of claim 12,
The aggregation phenomenon of the? -Cyclodextrin polymer of the hyperbranched network structure is reduced by the alginate, and the electrostatic repulsion between the alginate is reduced by the? -Cyclodextrin polymer. cathode. A lithium ion battery comprising the lithium ion battery anode according to claim 9.

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