At present,carbon materials are considered to be the most promising supercapacitor materials,such as one-dimensional carbon nanotubes(CNTs),carbon nanofibers(CFs)and graphene,which are widely used in electric double layer capacitors.nanocellulose can be directly mixed with CNT and graphene materials to form independent electrodes.the Nanocellulose plays a role in improving the hydrophilic property and increasing the utilization rate of the mesopores of the electrode material。

Bacterial cellulose(BC)is composed of cellulose with a diameter of 3~4 nm by biotechnology,which has the characteristics of high purity,high crystallinity(up to 95%)and high degree of polymerization(2000~8000)^[4,5][6]。 In 2012,Kang et al.Developed a BC/CNT paper electrode for flexible supercapacitors by vacuum filtration^[7]。 Due to the winding structure of CNT and BC substrate,The paper electrode has good flexibility and continuous conductive path.the Prepared BC/CNT film has no delamination phenomenon during hundreds of repeated bending processes,and shows good mechanical stability.the supercapacitor assembled with the BC/CNT film electrode showed a high specific capacitance of 50.5 F/G(Figure 2A).In 2015,Jost et al.prepared a nanofiber-based flexible supercapacitor by weaving technology^[8]。 Activated carbon(AC)was added to the expanded cellulose yarn during the welding process.the assembled supercapacitor has a high carbon mass loading(0.62 mg/cm)and a high capacitance(37 mF/cm).cellulose microfibers in plant cell walls can be separated by mechanical decomposition,and the resulting nanofibers are usually called cellulose nanofibers(CNF),which have the advantages of low density,low thermal expansion coefficient,high strength,high stiffness,and easy deformation^[9,10]。 In 2020,Santos et al.Reported a double-walled and triple-walled carbon nanotube(FWCNT)combined with CNF Buckypaper(BP)composite(Figure 2B)^[11]。 The resulting composite(BP/FWCNT@CNF)is fully flexible and moldable.The BP/FWCNT@CNF film maintains the structure of carbon nanotubes and has good wettability and conductivity.A high specific capacitance(380.8 F/G)at 1 A/G was obtained when hydroquinone/H₂SO₄was used as redox electrolyte.In 2019,Guan et al.Reported a porous graphene oxide(HRGO)/BC composite membrane^[12]。 the membrane has a three-dimensional honeycomb structure(Fig.2C),a tensile strength of up to 204 MPa,and can be bent,folded,knotted,and twisted.The specific capacitance of The supercapacitor with HRGO/BC electrode is as high as 65.9 F/G。

In addition,nanocellulose is also commonly used In separators and electrolytes for supercapacitors due to its strong mechanical properties,wettability,and high porosity.In 2016,Kim et al.Reported a nanocellulose separator with a bilayer nanostructure^[13]。 the membrane was composed of terpyridine(TPY)functionalized CNF as a surface layer and electrospun polyvinylpyrrolidone/polyacrylonitrile as a support layer.the nanocellulose-based separator assembled by the supercapacitor can substantially improve the cycle performance,and the capacity retention rate after 100 cycles at high temperature is about 80%,while the capacity retention rate of the commercial polypropylene/polyethylene/polypropylene separator after 100 cycles at high temperature is only 5%.In 2018,Li et al.Reported a cellulose-based hydrogel membrane with hierarchical porosity and double-crosslinked structure^[14]。 Cellulose and polyacrylamide are crosslinked by polydopamine,and the mechanical properties of the hydrogel can be affected by adjusting the ratio of dopamine/acrylamide.The optimized sample C₄-DM-40 has excellent self-healing and mechanical properties,and the Fe³⁺functionalized hydrogel improves the sensitivity and conductivity of the hydrogel(Fig.3).Activated carbon was deposited on a C₄-DM-40 hydrogel membrane to assemble an integrated supercapacitor.The supercapacitor has a volumetric capacitance of 394.1 F/cm³and an areal capacitance of 275.8 mF/cm²（at 10 mV/s(Fig.3).In 2017,Zhao et al.Reported a renewable and transparent mesoporous cellulose membrane(mCel-membrane )^[15]。 The mCel membrane has high porosity(71.78%)and uniform mesopore distribution.The mCel membrane with saturated KOH as electrolyte exhibits good mechanical stability and flexibility with high ionic conductivity(325 mS/cm)and high electrolyte rejection(451.2 wt%)。

in general,nanocellulose materials are highly competitive In supercapacitors.Because of its low cost,high mechanical strength,good flexibility and high chemical stability,nanocellulose can effectively prevent the accumulation of carbon materials,significantly improve the hydrophilic performance of electrode materials and improve the utilization rate of mesopores of electrode materials。

more and More attention has been paid to the application of natural lignin biomass and its separated components In electrochemical energy storage(EES)devices.This is attributed to the excellent mechanical properties,intrinsic microstructure and chemical activity of Lignin,as well as the attractive characteristics of easy availability,sustainability and environmental friendliness.lignin biomass is a potential electrode material for sustainable development because of its relatively high carbon content and good conductivity after simple carbonization.lignin-derived materials can inherit the typical hierarchical porous structure of natural biomass,endowing the new materials with large specific surface area and porous structure,which is very beneficial for the realization of active electrode reaction and efficient ion transfer.the excellent mechanical strength of lignin when incorporated as a biopolymer in EES equipment gives these components high stability.in addition,the abundant oxygen-containing groups on the surface can provide effective hydrogen bonding with other components,which not only has high operational stability,but also has good electrolyte wettability^[16]。

Researchers have prepared carbon materials With different morphologies and chemical compositions from lignin through simple processes such as hydrothermal treatment,heteroatom doping,carbonization and activation.In these processes,variables such as carbonization temperature and activation method have a great influence on the properties of carbon materials.carbonization is usually carried out between 400℃and 1000℃.with the increase of carbonization temperature,pyrolysis intensifies,mass yield decreases,pore volume increases,thus obtaining higher porosity and specific surface area,and the degree of graphitization of carbon materials will be improved,thus obtaining better conductivity.In addition,the carbonization temperature also affects the content of nitroxide functional groups,which can act as active centers to provide additional pseudocapacitance.During the activation process,abundant channels and pores are formed on the surface and inside of the material,which can be adjusted by changing the mass ratio of the activator and the treatment time.Due to the etching effect of the activator,the hierarchical macro/meso/microporous structure and the high specific surface area enable the rapid transfer and effective storage of electrolyte ions,thereby improving the capacitance and rate performance of the electrode。

lignin-derived carbon materials with different structures can be prepared from various lignin products separated from natural lignin biomass.In 2017,Liu et al.Synthesized rod-like porous carbon from aniline-modified lignin,and its structural properties could be adjusted by carbonization temperature^[17]。 Lignin-derived 2D carbon nanosheets with oxygen content of 11 wt%were prepared by freeze-casting and carbonization methods.It exhibits a high specific capacitance of 281 F/G at 0.5 A/G,which is attributed to the pseudocapacitive contribution of oxygen heteroatoms.In 2018,Zhang et al.Prepared lignin porous carbon microspheres(HPCMs)by inverse dehydration,in which K₂CO₃acted as both a pH regulator and a template and activator during further carbonization^[18]。 the capacitance of the Prepared HPCMs electrode is 140 F/G in 0.05 A/G organic electrolyte.in the same year,Zhang et al.prepared nitrogen-doped layered 3D carbon rich in micropores,mesopores and interconnected macropores by hydrothermal crosslinking reaction and KOH activation,which showed a high specific capacitance of 440 F/G at 0.5 A/G^[19]。 in 2019,Chen et al.Prepared lignin-based porous carbon rich In mesopores and with a hybrid oxygen atom content of 16.5%by microwave one-step heating combined with humidified nitrogen,and obtained a high-performance supercapacitor^[20]。 as shown in Fig.4,in 2016,Zhang et al.Constructed a hierarchical porous nitrocarbon(HPNC)by using the lignin by-product produced in the bioethanol production process As the carbon precursor through hydrothermal treatment and activation^[21]。 HPNC has excellent supercapacitor application characteristics such as hierarchical bowl-shaped pore structure,large specific surface area and high conductivity.the specific capacitance is 312 F/G at 1 A/G and 254 F/G at 80 A/G,exhibiting a high rate capacity of about 80%.After 20 000 cycles at 10 A/G,98%capacitance retention and nearly 100%coulombic efficiency were maintained,showing excellent cycling stability and electrochemical performance.In addition,The energy density of HPNC-based supercapacitor is 44.7 Wh/kg at 73.1 kW/kg In ionic liquid(EMI-BF4)electrolyte.In 2017,Guo et al.obtained porous carbon with different KOH mass ratios by hydrothermal carbonization and chemical activation using enzyme hydrolysis lignin produced by butanol fermentation,and realized three-dimensional porous structure with high conductivity of 5.4 S/cm and excellent electrochemical performance^[22]。 high-performance carbon materials derived from lignin by-products can be used in supercapacitor electrodes,which is a potential High value-added product.Converting lignin into carbon materials for electrodes is a feasible way to make rational use of lignin。

Composite electrodes containing electrochemically active materials such as transition metal oxides and conductive polymers can obtain additional pseudocapacitance,resulting in higher capacitance,larger operating voltage window and higher energy density^[23]。 lignin biomass has been widely used in composite electrode materials for supercapacitors to prepare high-performance Pseudocapacitive electrodes due to its excellent mechanical properties and chemical activity.pseudocapacitive electrodes require a matrix to enhance conductivity and provide a porous framework,and lignin biomass-derived carbon materials show excellent performance when used as a matrix material.in 2018,Zhou et al.Prepared a lignin-derived layered mesoporous carbon nanosphere embedded with 11 wt%NiO nanoparticles in situ^[24]。 This carbon nanosphere has a specific surface area of 852 m²/g and a specific capacity of 508 F/G.In addition,in 2019,Fu et al.Synthesized lignin-derived carbon/zinc oxide(LDC/ZnO)composite by electrostatic self-assembly carbonization process,and the specific capacity was up to 193 F/G at 0.5 A/G^[25]。 Lignin-derived nanosheets encapsulate ZnO nanoparticles with high pore volume and large specific surface area.Since the porous structure of lignin-derived carbon matrix improves the electrical conductivity and ionic transfer,and provides a large interfacial area,better performance is usually obtained by using pseudocapacitive electrodes of lignin-derived carbon in supercapacitors.In the field of solid-state flexible semiconductors,higher requirements are put forward for substrate materials with high flexibility,high porosity and low cost.In 2020,Jha et Al.Prepared Al/AC/Lig-MnO₂anode by depositing MnO₂on the surface of AC with lignin as the substrate^[26]。 The specific capacity reaches 5.52 mF/cm²at 6.01 mA/G.In another case,lignin was combined with NiWO₄nanoparticles and Al substrate as the anode of Al/lig-NiWO₄,and the specific capacity reached 17.01 mF/cm²at 0.13 A/G.Lignosulfonate and poly(3,4-ethylenedioxythiophene)(PEDOT)were used as dopant and surfactant to prepare PEDOT/Lig biocomposites by oxidative,chemical and electrochemical polymerization^[27]。 the capacitance of the PEDOT/Lig electrode is 170 F/G,which is twice that of the pure PEDOT electrode because of the additional pseudocapacitance caused by the quinone group in lignin.Considering the hydroquinone/quinone redox cycle,lignin itself is a potential active pseudocapacitive material^[28]。 Therefore,the lignin-based substrate is beneficial to improve the electrochemical performance of supercapacitors。

hemicellulose is considered to be an ideal carbon source for the preparation of porous carbon sphere electrodes for supercapacitors by hydrothermal carbonization because of its abundant content,good hydrophilicity and easy degradation.Lin et al.Derived a porous activated carbon material from Hemicellulose and used it as an active material for electrodes^[29]。 After 5000 cycles,the specific capacitance at 1 A/G is 37.8 F/G,and the retention rate is 97.3%.The improvement of electrode performance is attributed to the porous structure and chemical activity of hemicellulose.Wang et al.Prepared hemicellulosic carbon microspheres by hydrothermal carbonization and activated them with different activators(KOH,K₂CO₃,Na₂CO₃,ZnCl₂）)to improve their electrochemical performance as supercapacitors^[30]。 The specific surface area of the activated carbon spheres is obviously improved.The carbon spheres activated with zinc chloride have high specific surface area（2025 m²/g）and pore volume（1.07 cm³/g）.In a three-electrode system,the specific capacitance of the supercapacitor electrode fabricated from zinc chloride-activated carbon spheres was as high as 218 F/G at 0.2 A/G in 6 M KOH solution.A symmetrical supercapacitor was assembled in 2 M Li₂SO₄electrolyte,and the hemicellulosic carbon spheres activated by ZnCl₂exhibited excellent electrochemical performance with high specific capacitance(137 F/G at 0.5 A/G),high energy density(15.4 Wh/kg)and good cycling stability(95%capacitance retention after 2000 cycles).Zhang et al.Used hemicellulose as the carrier to prepare graphitized porous carbon spheres for supercapacitor electrode materials by one-step carbonization process without template^[31]。 Compared with the traditional two-step method,this method is environmentally friendly,low energy consumption and less time-consuming.The prepared hemicellulosic porous carbon spheres have high nanosize,large specific surface area(1250 m²/g),and high graphitization degree,and exhibit excellent electrochemical properties,including high specific capacitance(262 F/G at 1.0 A/G)and excellent cycling stability(95%capacitance retention after 1000 cycles )。

Electronic devices are developing rapidly In the direction of small,green and integrated,and there is an urgent need for supporting energy supply systems to meet the practical application needs of intelligent communications,mobile health and other fields.Nanocellulose-based materials have good mechanical properties and electrochemical stability,and show great potential for application as electrodes,solid electrolytes,and separators in lithium-ion batteries.in 2014,Li et al.Prepared reduced graphene oxide(RGO)/CNF composites by wet spinning and carbonization^[32]。 the conductivity of the Prepared material is(649±60)S/cm,which can be used as the negative electrode of lithium ion battery.The discharge capacity of the anode is stable at 312 mAh/G.In 2020,Wang et al.prepared black phosphorus/nanocellulose composite anode by vacuum filtration method^[33]。 The black phosphorus/nanocellulose composite provides a three-dimensional mixed conductive network for the transport of lithium ions and electrons.The specific capacity of the material is as high as 1020.1 mAh/G at 0.1 A/G.In 2019,Cao et al.Prepared flexible MoS₂hybrid films with hierarchical structure using 2,2,6,6-tetramethylpiperidine-1-oxyl(TEMPO)-oxidized CNF as fiber skeleton and bio-based binder^[34]。 After the addition of carbon nanotubes and the carbonization process,the MoS₂based paper electrode was finally obtained,as shown in fig.5A.The flexible paper electrode assembled by carbonized CNF,carbon nanotubes and ultrathin MoS₂nanosheets has a specific capacity of up to 930 mAh/G.For lithium-ion battery cathodes,the most common active materials on the market today are LiMn₂O₄,LiCoO₂,and LiFePO₄,but their cycle life is still limited by severe structural degradation during repeated charge-discharge processes and slow electron and lithium-ion transport kinetic rates.Therefore,nanocellulose can be used as a flexible substrate and conductive material to assemble cathode composites to improve the ionic/electronic conductivity of the electrode,reduce stress/strain,and maintain the integrity of the electrode^[35,36]。 by mixing CNF,Wang et al.Constructed MXene films with topological structure By spin vapor method in 2020^[37]。 The MXene@CNF film has excellent mechanical strength and flexibility,exhibiting an interdigitated topology,as shown in Figure 5B.The assembled flexible Li-ion battery(MXene@CNF-Li film anode matched with flexible LiFePO₄/CNF cathode)exhibited excellent stability and high specific capacity.In 2018,Kuang et al.Reported a flexible conductive nanofiber network for high-load electrodes,in which negatively charged CNF anchored neutral carbon black nanoparticles^[38]。 The conductive nanofiber network combined with lithium iron phosphate(LFP)enables the construction of a highly loaded and compact electrode,which effectively shortens the ion transport pathway(Figure 5C).The interconnected nanopores act as an electrolyte,surrounding the electroactive material and conducting ions to the electrode.The volumetric energy density of the assembled flexible Li-LFP cell is up to 538 Wh/m³ 。

the separator is located between the anode and cathode of the lithium-ion battery,which prevents the anode and cathode from short-circuiting due to contact.electrolyte is the medium between the positive and negative electrodes in lithium-ion batteries,which provides a channel for the transmission of lithium ions in the battery.the nanocellulose-based separator/Electrolyte is able to provide high porosity to enhance the ion migration rate in electrochemical reactions.in 2020,Sun et al.Synthesized ZIF8 crystals on the surface of CNF by in-situ synthesis and prepared ZIF8-CNF composite separator^[39]。 the introduction of ZIF8 prevented the aggregation of CNF and made the pore distribution more uniform,and the porosity increased from 42%of the pure CNF membrane to 55%of the composite separator.the ZIF8-CNF composite separator not only has fast wetting speed and good surface wettability,which can reduce the internal resistance of the battery and the electrolyte filling time,but also shows excellent thermal stability(up to 200℃).the lithium-ion battery assembled with the ZIF8-CNF composite separator showed excellent cycling performance and discharge capacity retention.In the same year,Huang et al.Prepared TEMPO-oxidized bacterial cellulose membrane(TOBC membrane)for lithium-ion battery separator^[40]。 The TOBC membrane has sufficient porosity,good affinity with liquid electrolyte and lithium electrode,good electrolyte absorptivity and small interfacial resistance.In 2018,Wang et al.Prepared a flexible redox-active cellulose separator with a bilayer nanostructure^[41]。 The separator consists of a redox-active polypyrrole(PPy)supporting layer and a mesoporous insulating CNF layer(Fig.6).the PPy support layer adds additional capacity to The Li-ion battery and provides mechanical support to The CNF layer.The redox-active membrane is highly flexible,and no internal short circuits were observed during operation.gel and solid-state electrolytes can provide better portability and safety for lithium-ion batteries.In 2018,Xu et al.Prepared a high-strength internally crosslinked bacterial cellulose(BC)network as a Gel polymer electrolyte^[42]。 Hydroxyl groups,ether groups,and glycosidic bonds on The BC chain trap organic solvents and provide lithium ion channels,thereby improving ionic conductivity.the battery assembled with gel polymer electrolyte has good rate and cycle performance.In 2019,Du et al.Prepared an environmentally friendly and mechanically strong cellulose gel membrane^[43]。 The cellulose membrane containing 5%epichlorohydrin has a wider electrochemical stability window,a higher Li⁺transference number(0.82),a higher ionic conductivity（6.34×10³mS/cm）,a better electrode interfacial compatibility,and good thermal stability and mechanical strength.In 2018,Dong et al.Prepared a BC-loaded poly(vinyl methyl ether-maleic anhydride)(P(MVE-MA))multifunctional polymer electrolyte for 4.45 V-class LiCoO₂metal lithium batteries(Fig.7 a,B )^[44]。 As shown in Fig.7 C,the tensile strength of the obtained polymer electrolyte reaches 50 MPa,which is attributed to the hydrogen bonding between P(MVE-MA)and BC.Even at 60°C,the LiCoO₂metal lithium battery assembled with the polymer electrolyte showed high capacity retention(85%after 700 cycles )。

Lignin biomass resources have the advantages of High Carbon content and porous structure,which can be directly carbonized into carbon electrodes or current collectors without conductive agents.carbon materials prepared by pyrolysis,heteroatom doping and activation have good conductivity,rich electrolyte-electrode interface and stable structure.As mentioned in the previous subsection,the carbonization conditions have a great influence on the performance of electrode materials.the carbonization temperature and activation method can directly adjust the specific surface area and pore structure of lithium-ion batteries.the activation method determines the electrode-electrolyte interface and the migration of ions,which is very important for the capacity and rate characteristics of lithium-ion batteries.mechanical strength controlled by carbonization temperature is another important characteristic of electrode materials.high Mechanical strength can cope with large volume changes caused by lithium ion insertion,thus achieving low deformability to improve the stability of the electrode。

In 2018,Nowak et al.Synthesized lignin-based carbon fibers(LCFs)from kraft lignin,a by-product of pulping,by carbonization at different temperatures ranging from 1000 to 1700℃^[45]。 The advantages of using LCFs as anode materials for lithium-ion batteries are their good conductivity and mechanical integrity without conductive additives,current collectors,or binders,which are beneficial to improving the specific energy and energy density of lithium-ion batteries.The tensile strength and Young's modulus of LCFs decrease with the increase of carbonization temperature.The LCFs carbonized at 1000℃have the best mechanical properties,with the tensile strength of(628±106)MPa,the Young's modulus of(37±2)Gpa,the conductivity of more than 140 S/cm,and the maximum discharge capacity of 355 mAh/G,which are close to the values of commercial graphite electrodes.The electrical conductivity of LCFs increases with increasing carbonization temperature.However,the difference between the data of LCFs_1000℃and LCFs_1700℃is only 50 S/cm,which means that the carbonization temperature has little effect on the electrical properties.The conductivity of LCFs before and after galvanostatic charge-discharge remains almost unchanged,which indicates that the electrical properties can be maintained after cycling.Under full cell cycling(Fig.8),the discharge capacity after the third cycle was 97 mAh/G with a capacity retention of 97.8%.After prolonging the cycle time,the cycle capacity is more than 99%,and the capacity fading rate is 1.3%after 22 cycles,showing good electrical properties.Therefore,LCFs can be used as anode materials for lithium-ion batteries in a complete battery pack.In 2020,Xi et al.Reported the study of K₂CO₃activated lignin-derived porous carbon(LPC)materials with different lignin sources as electrode materials for lithium-ion batteries,and explored the effects of lignin sources on the structural,chemical,and electrochemical properties of LPC^[46]。 The results show that high molecular weight and low O/C ratio are beneficial to the degree of graphitization,but have a tendency to reduce the specific surface area.The specific surface area of the LPC prepared by enzymatic hydrolysis of lignin was 1680 m²/g,and the LPC had better electrochemical performance in lithium-ion batteries,with a capacity of 490 mAh/G at a current density of 200 mA/G.It can be seen that lignin is a promising precursor for conductive carbon materials.Lignin-derived carbon materials are combined with anode and cathode active materials,and have stable performance when used as current collectors and conductive substrates in lithium-ion batteries.In 2017,Chen et al.Prepared an ultra-thick 3D carbon skeleton current collector by direct carbonization of natural wood chips^[47]。 Carbon fibers well maintain the unique arrangement channels of natural wood,providing a continuous conductive network for the rapid transport of electrons and channels for the transport of ions.The conductivity and ion diffusion coefficient of the lithium iron phosphate material after infiltration into the microchannel reached 6.75 S/cm and 5.2×10^-11cm²/s,respectively.The electrode has a high active material loading of 60 mg/cm²,a discharge capacity of 7.6 mAh/cm²（(95 Ah/L by volume),and an energy density of 26 MWh/cm²（(323 Wh/L by volume)at 0.5 mA/cm²,and has small deformation and good cycle stability.In the same year,Hu et al.Synthesized binderless SiO_x/C composite lithium ion electrode of SiO_xand sulfate lignin by heat treatment at 600°C^[48]。 due to the flexibility of the lignin-derived carbon matrix,the composite electrode still maintained a current density of 200 mA/G and an initial capacity of about 900 mAh/G after 250 cycles.This is Due to the flexibility of the lignin-derived carbon matrix,which allows it to adapt to volume changes。

lignin and its derivatives have shown good application prospects as electrode binders for lithium ion batteries after modification because biopolymers usually contain abundant active oxygen-containing groups.Through free graft copolymerization with polyacrylate(PAA),Luo et AL.Prepared an alkali Lignin(AL)-derived water-soluble silicon anode binder,denoted as PAL NaPAA,in 2018^[49]。 the binder can adjust the inevitable volume change of silicon anode and maintain a high specific capacity of 1914 mAh/G after 100 cycles at 840 Ma/G.In order to develop high energy density lithium-ion batteries and solve the problem of continuous free radical attack caused by oxidative decomposition of carbonate-based cathode electrolyte.In 2019,mA et al.Studied this and prepared a renewable lignin binder containing a large number of phenol groups^[50]。 The binder can effectively scavenge free radicals,thereby inhibiting the oxidative decomposition of the electrolyte.The as-prepared LiNi_0.5Mn_1.5O₄(LNMO)cathode exhibited excellent stability with a capacity retention of 94.1%after 1000 cycles 。

Gel polymer electrolyte(GPE)is a new type of electrolyte combining polymer membrane and liquid electrolyte,which is an effective solution to the problems of traditional electrolyte leakage,flame and explosion.In 2016,Gong et al.Used lignin fiber and liquid electrolyte as raw materials to prepare green and environmentally friendly GPE by infiltration method^[51]。 The lignin-derived GPE membrane with a porous structure absorbed 230 wt%of the liquid electrolyte and maintained good strength with a lithium ion transference number of 0.85,as shown in Fig.9 a–C.In the Li/lignin-derived GPE/LiFePO₄half cell,the capacity reached 165 mAh/G(97%of the theoretical capacity).Lignin-derived carbon materials usually have a porous structure,which can provide efficient migration of electrolyte ions and electrons.When lignocellulose acts as a binder or a conductive matrix,the abundant oxygen-containing groups on its surface can enhance the binding with electrochemically active species,thus contributing to improved stability.In addition,the modification of active groups by lignin makes the derived materials have multifunctional synergistic effects,thus improving the performance of electrodes and GPEs 。

Overall,lignin proved to be an attractive renewable material for use as a conductive matrix,binder,and electrolyte for low-cost,high-energy-density lithium-ion batteries。

hemodialysis is a blood purification technique in which harmful substances,excess metabolic waste products,and electrolytes in the fluid are excreted outside the body during diffusion.Among the various materials used to prepare dialysis membranes,cellulose acetate membranes have the advantages of high transmittance,high strength,good elasticity,low cost,good biocompatibility,and high dialysis efficiency.Therefore,cellulose acetate membrane is the most commonly used material in Hemodialysis and has been commercialized^[58]。 in 1995,Ishihara et al.Improved the surface hemocompatibility of cellulose hemodialysis membrane by grafting poly[2-methacryloyloxyethyl phosphorylcholine]on the surface of water-soluble cellulose,as shown In Fig.10^[59]。 In 2006,Idris et al.Studied the effects of different molecular weights of polyethylene glycol(PEG 200,400,600)and the amount of polyethylene glycol added on the performance of dialysis membranes^[60]。 it was found that low dosage(less than 5%)and low molecular weight(200)of PEG could improve the clearance rate of urea,and high molecular weight of PEG could improve the viscosity of the coating.the results of human blood experiments show that the prepared dialysis membrane has good biocompatibility,because It can effectively remove uremic toxins from human blood and prevent the diffusion of human proteins from the blood side.in 2013,Qiu et al.Reported a pH-and temperature-responsive membrane with poly(N-isopropylacrylamide)(PNIPAAAm)and poly[2-(diethylamino)ethyl methacrylate](PDEAEMA)simultaneously grafted from different sides of a cross-linked cellulose membrane,which has great potential applications In drug delivery and water treatment^[61]。 In addition,cellulose acetate membrane materials can also be prepared by electrospinning.Ma et al.Used cellulose acetate as raw material to prepare regenerated cellulose nanofiber membrane by electrospinning,subsequent heat treatment and alkalization,and then modified functional protein A/G on the surface of the membrane for purification of immunoglobulin G(IgG)^[62]。 the results showed that The affinity membrane had a capture capacity of 18 G/mg and a strong binding specificity for IgG molecules。

Hydrogel is a kind of hydrophilic polymer with three-dimensional network,which contains a large amount of water and is insoluble.It has the advantages of non-toxicity,high drug loading,biodegradability and biocompatibility,good support scaffold and oriented structure.Therefore,hydrogels have great potential applications in biotechnology and biomaterials,such as tissue engineering scaffolds,drug delivery,energy devices and so on.Cellulose hydrogels are generally prepared by two methods:(1)chemical polymerization,such as microwave irradiation polymerization and aqueous solution polymerization;(2)Physical synthesis method。

In 2016,Liu et al.Prepared a composite hydrogel by chemical modification of carboxymethyl fiber with bamboo shoot cellulose^[63]。 Sodium salicylate was used as a model drug to study the adsorption and release behavior of the hydrogel in simulated intestinal(pH 7.4)and gastric(pH 1.8)environments.The release rate of the prepared composite hydrogel in simulated intestinal fluid(63.09%after 380 min)was higher than that in gastric fluid(22.09%after 400 min).The potential application of the composite hydrogel in controlling drug release in different environmental conditions or human organs is shown.In 2018,Liu et al.Added silver amide nanoparticles（AgNH₂NPs）and gelatin(G)to CNF^[64]。 When 0.5 mg/mL of Ag-NH₂NPs was added,the CNF/G/Agwater Gel showed good mechanical properties,biocompatibility and wound healing effect.After 14 days of treatment,the wound healing rate and survival rate were close to 90%and 83.3%,respectively 。

According to the detection principle,biosensors can be divided into optical biosensors,electrochemical biosensors and piezoelectric biosensors.Cellulose-based biosensors are flexible,portable,disposable,and highly sensitive^[65]。 In 2014,Lawrence et al.Reported a"green"cellulose paper based on an amperometric biosensor for glucose,immobilizing glucose oxidase by a simple adsorption method^[66]。 The linear dynamic calibration range of the sensor was 1–5 mM glucose（r²=0.971）,the lower detection limit was 0.18 mM,and the signal retention was 98%after 4 months.In the same year,Schyrr et al.Prepared a biosensor-derived porous cellulose nanocrystal-polyvinyl alcohol scaffold(Fig.11 )^[67]。 The sensor membrane is capable of instantaneously changing fluorescence emission intensity In response to changes in pH.in 2015,Sadasivuni et al.Developed a partially transparent flexible temperature sensor made of a composite film of graphene and cellulose^[68]。 the relative capacitance of this composite is a function of temperature,showing a linear behavior in The temperature range from 25 to 80°C.Mahadeva et al.Reported a cellulose-based humidity sensor.The structure of cellulose remained unchanged after nanoscale polypyrrole(PPy)was introduced into the cellulose membrane by in-situ polymerization^[69]。 The nanocomposite exhibits a high capacitance that is affected by changes in humidity.Maniruzzaman et al.Prepared titania-cellulose hybrid nanocomposite by mixing nano-titania with cellulose solution^[70]。 the composite material has The advantages of low price and disposability,and can be prepared into a flexible biosensor。

xylan-based hemicellulose has been widely reported as a suitable material for the preparation of thin films.Peng et al.Successfully incorporated cellulose nanofibers(CNF)into Xylan-rich hemicellulose to obtain nanocomposite membranes^[71]。 The nanocomposite film has good mechanical properties and thermal stability.Hartman et al.Reported hemicellulose acetylgalactomannan-derived oxygen membranes that exhibited high resistance to moisturizing conditions^[72]。 in addition,galactomannan has been used to prepare transparent,waterproof,and flexible films.Because xylan is soluble in the colon but not in the stomach,Silva et al.Prepared a magnetic microparticle coated with xylan to monitor gastrointestinal peristalsis^[73]。

Hemicellulose,the second most abundant polysaccharide in plants,has been used in the preparation of hydrogels due to its economic,biocompatible,non-toxic and biodegradable properties。

Peng et al.Prepared a series of novel xylan-rich hemicellulosic ionic hydrogels^[74]。 Free radical graft copolymerization of acrylic acid and xylan-rich hemicellulose was carried out using ammonium persulfate/N,N,N′,N′-tetramethylethylenediamine as redox initiation system and N,N-methylenebisacrylamide as crosslinking agent.the results showed that The hemicellulose-rich ionic hydrogel with xylan had a rapid response to ions,pH and organic solvents,and a high water absorption capacity.In 2012,Peng et al.Also reported a new porous adsorbent obtained by graft copolymerization of xylan-rich hemicellulose and acrylic acid(AA)^[75]。 Fig.12 shows the morphological changes of xylan-based hemicellulose-g-AA hydrogel during the adsorption process of metal ions in solution at different time periods.The hydrogel exhibited high adsorption capacity(859,495 and 274 mg/G)and high regeneration efficiency for Pd²⁺,Cd²⁺and Zn²⁺ 。

in recent years,lignin-based composite membranes have attracted more and more attention In the biomedical field because of their good biocompatibility and non-toxicity,which can be used as wound dressing materials,tissue engineering scaffolds,drug carriers and so on。

Ag-doped hydroxyapatite and lignin composite films were prepared by pulsed laser evaporation.the results of microbiological evaluation showed that the composite film inhibited the formation of bacterial and fungal biofilms,and the intensity of antibacterial activity was positively correlated with the content of lignin and silver.Moreover,the film has weak cytotoxicity to human bone marrow mesenchymal stem cells,which provides an important basis for the development of implantable biomaterials.Kai et al.Synthesized a series of lignin-grafted poly(methyl methacrylate)(PMMA)copolymers by atom transfer radical polymerization to improve the brittleness and dispersibility of lignin^[76]。 Then the lignin copolymer was blended with polycaprolactone to prepare nanofiber composites by electrospinning.the Prepared lignin-based composite has biocompatibility and does not affect the proliferation,adhesion and interaction of human dermal fibroblasts.Similarly,Salami et al.prepared polycaprolactone/lignin nanocomposite,which has the characteristics of simulating extracellular matrix conditions and can be used to construct soft tissue engineering scaffolds^[77]。 cell proliferation is affected by the lignin content in the composite,with suitable lignin content(10–30 wt%)promoting Cell proliferation and higher lignin content(50 wt%)showing an inhibitory effect,so it is crucial to optimize the loading of lignin to balance cytotoxicity。

Lignin-based hydrogels are three-dimensional networks of cross-linked hydrophilic molecules that can absorb large amounts of water or drugs in their structure。

In 2018,Larra Larrañeta et al.Synthesized lignin hydrogel by esterification of polyethylene glycol and poly(methyl vinyl ether-maleic acid)under microwave irradiation^[78]。 the Prepared samples showed that the water absorption was up to 500%at lignin content between 25%and 45%,and the modified lignin hydrogel was able to be administered for up to 4 days.In 2019,Zhou et al.prepared lignin-based targeted drug delivery nanoparticles by loading doxorubicin hydrochloride^[79]。 Lignin nanoparticles were prepared by a layer-by-layer self-assembly method with the addition of iron oxide（Fe₃O₄）a nd folic acid.The surface morphology showed that the surface of the lignin nanoparticles was uniformly covered with a layer of iron oxide and folic acid,which enhanced the ability of the hydrogel to absorb Henrietta Lacks cells(used to study hydroxyurea therapy for some blood cancers and sickle cell anemia).During the self-assembly process,doxorubicin hydrochloride was easily loaded on lignin nanoparticles,and the loading rate was 67.5%±6%.The loaded lignin nanoparticles have good sustained-release effect and high anticancer activity.In 2019,Ravishankar et al.Formed a biocompatible hydrogel through the cross-linking of chitosan and lignin for wound healing^[80]。 the hydrogel was synthesized by mixing chitosan solution with alkaline lignin solution,and the phenolic oxygen group of lignin and the ammonium group of chitosan were crosslinked.the hydrogel provides a suitable surface for cell attachment and rapid cell growth.Mouse fibroblasts were studied,and it was observed that there was good cell migration in the presence of the hydrogel,and the hydrogel had the advantages of cheapness and high reproducibility,indicating that the hydrogel had broad prospects in the direction of wound healing。