CMC, with the strong cohesion, good heat stability, electrical conductivity and electrochemistry property, makes the active substance and electrolyte form the even and dispersive paste, and takes the hydrogen bond effect with the silicon, therefore, it is not only widely used as the binder of cathode and anode, gel for cathode protection, but also widely applied in the silicon base electrode and graphite modification.
1. Application in binder of cathode and anode
Binder has the great impact on the electrode property of the battery. Appropriate binder can effectively change the general performance of the electrode, and make the active substance, conductive agent and current collector contact evenly, and enhance the completeness of the electrode. As the binder, CMC can be widely applied in the kinds of electrode material such as lithium battery, natural graphite, mcmb, lithium titanate, tin-based, silicon-based negative electrode material and iron-phosphate-based lithium cathode material etc. It greatly enhances the battery capacity, circulation stability and lifespan circulation. CMC shows the effect in the binder of cathode and anode as follows:
*bind the active substance, conductive agent and current collector together;
*Fix firmly electrode material on the current collector;
*Excellent conductivity reduces the impedance between electrode material and current collector;
*Excellent electrochemistry property extends the battery capacity;
*Good heat stability enhances the battery circulation stability and lifespan circulation;
*Good electrochemistry stability, and stable with the electrode material and electrolyte;
*Release the expansion and shrink during the li-battery in charging or discharging;
*Less usage, strength bind, low load discharging;
*Safety, eco-friendly, and low cost.
2. Application in gel for cathode protection
As the gel, CMC can make the active substance and electrolyte form the even and dispersive paste, maintain the electrolyte evenly around the active granule, and make the electrolyte evenly and sufficiently cover the active granule surface when battery discharges, meanwhile, it prevents the active granule and electrolyte in the storage from being unevenly settled. Furthermore, it promotes the contact effect between active granule, active substance and collector, and prevents the battery from voltage abnormal dropping when the battery is suffered from the shake or during use. CMC which is applied in gel for cathode protection will show the effect as follows:
*Good viscosity and liquid absorption, and high linearity tractility;
* With a certain viscosity and effectively prevent the battery active substance from being dehydated.
*Good stability, less layering, and good property for battery storage;
*Enhance the electrolyte absorption rate and reduce the electric resistance;
*Use under the normal temperature, and avoid the fluctuation in the end of the terminal voltage of intermittence discharging;
*Good liquid retention, and keep the good performance when the battery is under the normal temperature or high temperature;
*little swaying under the circumstance of negative electrode, and battery stable performance after falling and shaking;
*mix with sodium acrylate and greatly enhance the high current discharge performance of the battery
3. Application in silicon-based electrode
CMC used in the silicon-based electrode, besides the heat stability, conductivity and electrochemisty, the strong hydrogen bond exists between CMC and silicon. Hydrogen bond has the self-recovery, and it can adjust the stress which continuously enlarge during the circle process of the material and so that it can maintain the stability of the material structure, and keep the capacity over 1000mAh/g during at least 100 times circulation, and the coulombic efficienty reaches 99.9%. CMC which is applied in silicon-based electrode will show the effect as follows:
*With the strong shear-thinning property, CMC can adjust the rheoloty of the slurry;
*Excellent circulation, primitive reversible capacity and better capacity retention;
*Effectively cushion the change of the volume swelling of the silicon-based electrode, and improve the electrode reversibility;
*With the double optimization to mechanics stability and the chemistry stability, CMC promotes to form the SEI film;
* CMC impacts on silicon granule, and reduces the damages for silicon-based electrode volume swelling;
*Effectively inhibit the side-reaction between high reactive Li-Si alloy and electrolyte;
*Use with other gel binders, and enhance the binding strength and activation properties.
4. Application in graphite modification
With the good coating effect to the natural graphite, CMC can effectively improve its surface quality, inhibit the strong reduction reaction of electrolyte on the surface, prevent the solvation ion from being into the graphite layer leading to the structure delamination, enhance the electrochemistry property of the natural graphite, and effectively produce the exfoliation phenomenon in the process of charging or discharging of the graphite. Therefore, it effectively increases the circulation stability of the carbon composite and improve the battery stability and performance. CMC which is applied in graphite modification will show the effect as follows:
*The formed resin carbon can make the lithium ion diffuse to internal of the graphite through the resin carbon;
*Prevent the solvation and lithium ion from being embedded together, and weaken the reduction reaction which the solvent molecule impacts on the electrode;
*Graphite circulation property is obviously increased after coating treatment, and effectively inhibit the capacity reduction of graphite;
*Effectively increase the retention rate of discharging platform and discharging capacity.
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Type
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Degree of Substitution
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Application Fields
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Low D.S.
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0.60-0.80
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Used as binder, gel, silicon-based additives and graphite modification.
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Conventional D.S.
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0.80-1.00
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High D.S.
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≥1.00
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