With the use of lithium batteries, battery performance continues to decay, mainly as capacity decay, internal resistance increase, power drop, etc. The change of battery internal resistance is affected by various usage conditions such as temperature and discharge depth. Therefore, the factors that affect the internal resistance of the battery are described in terms of battery structure design, raw material performance, manufacturing process and use conditions.

Resistance yog qhov kev tawm tsam uas lub roj teeb lithium tau txais thaum lub sijhawm tam sim no ntws hauv lub roj teeb thaum nws ua haujlwm. Feem ntau, cov kev tiv thaiv sab hauv ntawm lithium roj teeb tau muab faib ua ohmic sab hauv tsis kam thiab polarization sab hauv tsis kam. Lub ohmic sab hauv tsis kam yog tsim los ntawm cov khoom siv electrode, electrolyte, diaphragm tsis kam thiab kev sib cuag ntawm txhua qhov chaw. Polarization internal resistance yog hais txog kev tiv thaiv los ntawm polarization thaum lub sij hawm electrochemical cov tshuaj tiv thaiv, nrog rau electrochemical polarization internal kuj thiab concentration polarization internal kuj. Lub ohmic sab hauv tsis kam ntawm lub roj teeb yog txiav txim los ntawm tag nrho cov conductivity ntawm lub roj teeb, thiab lub polarization nyob rau hauv tsis kam ntawm lub roj teeb yog txiav txim los ntawm cov khoom theem diffusion coefficient ntawm lithium ions nyob rau hauv lub electrode active khoom.

Ohm tsis kam

Lub ohmic tsis kam yog feem ntau muab faib ua peb ntu, ib qho yog ionic impedance, lwm yam yog hluav taws xob impedance, thiab qhov thib peb yog hu rau impedance. Peb cia siab tias qhov kev tiv thaiv sab hauv ntawm lithium roj teeb tsawg li tsawg tau, yog li peb yuav tsum tau siv cov kev ntsuas tshwj xeeb los txo qis ohmic sab hauv tsis kam rau peb yam khoom no.

Ion impedance

Lithium roj teeb ion tsis kam yog hais txog kev tiv thaiv kev sib kis ntawm lithium ions hauv lub roj teeb. Nyob rau hauv lub lithium roj teeb, lithium ion migration ceev thiab electron conduction ceev ua si ib qho tseem ceeb luag hauj lwm, thiab ion kuj yog feem ntau cuam tshuam los ntawm cov khoom zoo thiab tsis zoo electrode, lub separator, thiab electrolyte. Txhawm rau txo cov ion impedance, koj yuav tsum ua cov hauv qab no:

Xyuas kom meej tias cov ntaub ntawv zoo thiab tsis zoo thiab cov electrolyte muaj qhov ntub dej zoo

Nws yog ib qho tsim nyog los xaiv qhov tsim nyog compaction ntom thaum tsim cov ncej ncej. Yog hais tias lub compaction ceev yog loj heev, lub electrolyte tsis yooj yim rau infiltrate, uas yuav ua rau kom cov ion kuj. Rau cov ncej tsis zoo, yog tias SEI zaj duab xis tsim rau saum npoo ntawm cov khoom siv thaum lub sij hawm thawj zaug thiab tawm yog tuab heev, nws tseem yuav ua rau kom cov ion tsis kam. Lub sijhawm no, nws yog ib qho tsim nyog los kho cov txheej txheem tsim ntawm lub roj teeb los daws nws.

Kev cuam tshuam ntawm electrolyte

Cov electrolyte yuav tsum muaj qhov tsim nyog concentration, viscosity thiab conductivity. Thaum lub viscosity ntawm cov electrolyte siab dhau lawm, nws tsis yog conducive rau infiltration ntawm cov electrolyte thiab active khoom ntawm lub zoo thiab tsis zoo electrodes. Nyob rau tib lub sij hawm, cov electrolyte kuj xav tau ib tug tsawg concentration, siab heev concentration kuj tsis conducive rau nws ntws thiab infiltration. Lub conductivity ntawm electrolyte yog qhov tseem ceeb tshaj plaws cuam tshuam rau ion kuj, uas txiav txim siab tsiv teb tsaws ntawm ions.

Kev cuam tshuam ntawm diaphragm ntawm ion kuj

The main influencing factors of the diaphragm on the ion resistance are: electrolyte distribution in the diaphragm, diaphragm area, thickness, pore size, porosity, and tortuosity coefficient. For ceramic diaphragms, it is also necessary to prevent ceramic particles from blocking the pores of the diaphragm, which is not conducive to the passage of ions. While ensuring that the electrolyte is fully infiltrated into the diaphragm, there should be no excess electrolyte remaining in it, which reduces the efficiency of the electrolyte.

Electronic impedance

Muaj ntau yam cuam tshuam ntawm hluav taws xob impedance, uas tuaj yeem txhim kho los ntawm cov khoom xws li cov khoom siv thiab cov txheej txheem.

Daim phiaj zoo thiab tsis zoo

The main factors affecting the electronic impedance of the positive and negative plates are: the contact between the active material and the current collector, the factors of the active material itself, and the parameters of the plate. The active material should be in full contact with the current collector surface, which can be considered from the current collector copper foil, aluminum foil base material, and the adhesion of the positive and negative electrode pastes. The porosity of the living material itself, the by-products on the surface of the particles, and the uneven mixing with the conductive agent, etc., will cause the electronic impedance to change. Polar plate parameters such as the density of living matter is too small, the gap between the particles is too large, which is not conducive to electron conduction.

Diaphragm

Lub ntsiab yam tseem ceeb uas cuam tshuam rau cov hluav taws xob impedance ntawm lub diaphragm yog: diaphragm thickness, porosity, thiab los ntawm cov khoom nyob rau hauv tus nqi thiab tso tawm. Thawj ob yog yooj yim to taub. Tom qab lub roj teeb yog disassembled, ib txheej tuab ntawm cov khoom xim av feem ntau pom nyob rau hauv lub separator, nrog rau cov graphite tsis zoo electrode thiab nws cov tshuaj tiv thaiv los ntawm cov khoom, uas yuav thaiv lub diaphragm pores thiab txo cov kev pab cuam lub neej ntawm lub roj teeb.

Tam sim no collector substrate

Cov khoom siv, tuab, dav ntawm cov khoom siv tam sim no thiab qib kev sib cuag nrog cov tabs tag nrho cuam tshuam rau cov hluav taws xob impedance. Tus neeg sau tam sim no yuav tsum xaiv lub substrate uas tsis tau oxidized thiab passivated, txwv tsis pub nws yuav cuam tshuam rau impedance. Tsis zoo vuam ntawm tooj liab thiab txhuas ntawv ci thiab tabs kuj yuav cuam tshuam rau hluav taws xob impedance.

Hu tau tiv

Kev tiv thaiv kev sib cuag yog tsim los ntawm kev sib cuag ntawm tooj liab thiab txhuas ntawv ci thiab cov khoom siv, thiab kev saib xyuas yuav tsum tau them rau qhov adhesion ntawm qhov zoo thiab tsis zoo electrode pastes.

Polarized internal kuj

Thaum tam sim no dhau los ntawm cov electrodes, qhov tshwm sim uas cov electrode muaj peev xwm deviates los ntawm qhov sib npaug electrode muaj peev xwm hu ua electrode polarization. Polarization muaj xws li ohmic polarization, electrochemical polarization thiab concentration polarization. Polarization tsis kam yog hais txog kev tiv thaiv sab hauv los ntawm polarization ntawm qhov zoo electrode thiab tsis zoo electrode ntawm lub roj teeb thaum lub sij hawm cov tshuaj tiv thaiv electrochemical. Nws tuaj yeem cuam tshuam qhov sib xws ntawm lub roj teeb, tab sis nws tsis haum rau kev tsim khoom vim muaj kev cuam tshuam ntawm kev ua haujlwm thiab txoj kev. Internal polarization kuj tsis tas li, thiab nws hloov nrog lub sij hawm thaum lub sij hawm them nyiaj thiab tawm cov txheej txheem. Qhov no yog vim hais tias muaj pes tsawg leeg ntawm cov khoom siv, cov concentration thiab kub ntawm electrolyte hloov tas li. Lub ohmic sab hauv tsis kam ua raws li Ohm txoj cai, thiab polarization sab hauv kuj nce nrog qhov nce ntawm qhov ceev tam sim no, tab sis nws tsis yog kev sib raug zoo. Nws feem ntau nce linearly raws li lub logarithm ntawm qhov ceev tam sim no nce.

Tus qauv tsim kev cuam tshuam

Nyob rau hauv lub roj teeb qauv tsim, ntxiv rau riveting thiab vuam ntawm lub roj teeb qauv nws tus kheej, tus naj npawb, qhov loj, thiab qhov chaw ntawm lub roj teeb tabs ncaj qha cuam tshuam rau sab hauv ntawm lub roj teeb. Rau ib qho twg, nce tus naj npawb ntawm cov tabs tuaj yeem txo qhov kev tiv thaiv sab hauv ntawm lub roj teeb. Txoj hauj lwm ntawm cov tabs kuj cuam tshuam rau sab hauv ntawm lub roj teeb. Qhov kev tiv thaiv sab hauv ntawm lub qhov txhab roj teeb nrog txoj hauj lwm tab ntawm lub taub hau ntawm qhov zoo thiab qhov tsis zoo ntawm cov ncej yog qhov loj tshaj plaws. Piv nrog rau cov roj teeb lub qhov txhab, lub roj teeb laminated yog sib npaug rau ntau lub roj teeb me me nyob rau hauv tib lub sijhawm. , Nws sab hauv kuj yog me dua.

Cov khoom siv raw cuam tshuam kev ua haujlwm

Positive and negative active materials

Hauv cov roj teeb lithium, cov khoom siv hluav taws xob zoo yog cov lithium cia sab, uas txiav txim siab qhov ua tau zoo ntawm lithium roj teeb. Cov khoom zoo electrode feem ntau txhim kho cov hluav taws xob conductivity ntawm cov khoom los ntawm txheej thiab doping. Piv txwv li, doping nrog Ni txhim khu lub zog ntawm PO daim ntawv cog lus, stabilizes tus qauv ntawm LiFePO4 / C, optimizes lub cell ntim, thiab muaj peev xwm txo tau tus nqi hloov ntawm cov khoom zoo electrode. Qhov tseem ceeb ntawm kev ua kom polarization, tshwj xeeb tshaj yog kev ua kom polarization ntawm qhov tsis zoo electrode, yog lub ntsiab yog vim li cas rau qhov loj polarization. Txo qhov loj me me ntawm qhov tsis zoo electrode tuaj yeem txo qhov active polarization ntawm qhov tsis zoo electrode. Thaum cov khoom theem particle loj ntawm qhov tsis zoo electrode yog txo los ntawm ib nrab, lub active polarization yuav txo tau los ntawm 45%. Yog li ntawd, nyob rau hauv cov nqe lus ntawm lub roj teeb tsim, kev tshawb fawb txog kev txhim kho cov ntaub ntawv zoo thiab tsis zoo lawv tus kheej kuj tseem yog qhov tseem ceeb.

Conductive agent

Graphite thiab carbon dub tau siv dav hauv cov roj teeb lithium vim lawv cov khoom zoo. Piv nrog rau graphite-raws li conductive tus neeg saib xyuas, qhov zoo electrode nrog carbon dub-raws li conductive tus neeg saib xyuas muaj kev ua tau zoo roj teeb tus nqi, vim graphite-raws li conductive tus neeg saib xyuas muaj ib tug flaky particle morphology, uas ua rau ib tug loj nce nyob rau hauv pore tortuosity ntawm tus nqi loj, thiab Li kua theem diffusion yog ib qho yooj yim tshwm sim Qhov tshwm sim uas cov txheej txheem txwv lub peev xwm tawm. Lub roj teeb nrog CNTs ntxiv tau qis dua sab hauv, vim hais tias piv rau qhov sib cuag ntawm graphite / carbon dub thiab cov khoom siv, cov fibers carbon nanotubes yog nyob rau hauv kab sib cuag nrog cov khoom siv, uas tuaj yeem txo qhov cuam tshuam ntawm lub roj teeb.

Tus sau tam sim no

Txo qhov cuam tshuam ntawm kev sib txuas ntawm cov khoom siv tam sim no thiab cov khoom siv thiab kev txhim kho lub zog sib txuas ntawm ob yog qhov tseem ceeb los txhim kho kev ua haujlwm ntawm lithium roj teeb. Txheej txheej txheej txheej txheej txheej txheej ntawm aluminium ntawv ci thiab kev kho corona ntawm cov ntawv txhuas tuaj yeem txo qhov cuam tshuam cuam tshuam ntawm lub roj teeb. Piv nrog rau cov ntawv txhuas zoo tib yam, kev siv cov pa roj carbon-coated aluminium ntawv tuaj yeem txo qhov kev tiv thaiv sab hauv ntawm lub roj teeb li ntawm 65%, thiab tuaj yeem txo qhov nce hauv kev tiv thaiv sab hauv ntawm lub roj teeb thaum siv. Lub AC sab hauv tsis kam ntawm corona kho aluminium ntawv nyiaj tuaj yeem txo los ntawm 20%. Nyob rau hauv feem ntau siv 20% ~ 90% SOC ntau yam, tag nrho DC sab hauv kuj tseem me me thiab qhov nce yog maj mam me me raws li qhov tob ntawm qhov paug nce.

Diaphragm

The ion conduction inside the battery depends on the diffusion of Li ions in the electrolyte through the porous diaphragm. The liquid absorption and wetting ability of the diaphragm is the key to forming a good ion flow channel. When the diaphragm has a higher liquid absorption rate and porous structure, it can be improved. Conductivity reduces battery impedance and improves battery rate performance. Compared with ordinary base membranes, ceramic diaphragms and rubber-coated diaphragms can not only greatly improve the high temperature shrinkage resistance of the diaphragm, but also enhance the liquid absorption and wetting ability of the diaphragm. The addition of SiO2 ceramic coating on the PP diaphragm can make the diaphragm absorb liquid The volume increased by 17%. Coating 1μm PVDF-HFP on the PP/PE composite diaphragm, the liquid absorption rate of the diaphragm is increased from 70% to 82%, and the internal resistance of the cell is reduced by more than 20%.

Los ntawm cov txheej txheem ntawm kev tsim khoom thiab kev siv cov xwm txheej, cov yam ntxwv uas cuam tshuam rau sab hauv ntawm lub roj teeb feem ntau suav nrog:

Cov txheej txheem txheej txheem cuam tshuam

Pulping

Lub uniformity ntawm slurry dispersion thaum sib tov cuam tshuam seb tus neeg sawv cev conductive yuav uniformly dispersed nyob rau hauv lub active khoom nyob rau hauv kev sib cuag nrog nws, uas muaj feem xyuam rau lub internal kuj ntawm lub roj teeb. Los ntawm kev ua kom lub siab ceev dispersion, lub uniformity ntawm slurry dispersion tuaj yeem txhim kho, thiab lub zog sab hauv ntawm lub roj teeb yuav me dua. Los ntawm kev ntxiv cov surfactant, qhov sib xws ntawm kev faib tawm ntawm cov khoom siv hluav taws xob hauv electrode tuaj yeem txhim kho, thiab electrochemical polarization tuaj yeem txo qis thiab qhov nruab nrab tawm hluav taws xob tuaj yeem nce ntxiv.

Txheej

Qhov ntom ntom ntawm cheeb tsam yog ib qho tseem ceeb ntawm kev tsim roj teeb. Thaum lub roj teeb muaj peev xwm tsis tu ncua, nce qhov ntom ntom ntawm cov ncej ncej yuav ua rau txo qis tag nrho qhov ntev ntawm cov khoom siv tam sim no thiab cov diaphragm, thiab ohmic kuj ntawm lub roj teeb yuav txo qis raws li. Yog li ntawd, nyob rau hauv ib tug tej yam ntau yam, Lub internal kuj ntawm lub roj teeb yuav txo tau raws li lub cheeb tsam ntawm lub ceev nce. Kev tsiv teb tsaws thiab kev sib cais ntawm cov kuab tshuaj molecules thaum txheej txheej thiab ziab yog ze ze rau qhov kub ntawm qhov cub, uas cuam tshuam ncaj qha rau kev faib cov binder thiab conductive tus neeg sawv cev hauv cov ncej, thiab tom qab ntawd cuam tshuam rau kev tsim cov kab hluav taws xob hauv cov ncej. Yog li ntawd, txheej txheem txheej thiab ziab kub kub kuj yog ib qho tseem ceeb rau kev ua kom zoo ntawm cov roj teeb.

dov

Rau ib qho twg, lub zog sab hauv ntawm lub roj teeb txo qis thaum lub compaction ceev nce. Vim tias qhov compaction ceev nce, qhov kev ncua deb ntawm cov khoom siv raw khoom txo qis. Qhov kev sib cuag ntau dua ntawm cov khoom, qhov txuas txuas txuas ntxiv thiab cov channel ntau dua, thiab cov roj teeb impedance txo. Kev tswj ntawm compaction ceev yog ua tiav los ntawm dov thickness. Qhov sib txawv dov thicknesses muaj kev cuam tshuam ntau dua rau kev ua haujlwm sab hauv ntawm lub roj teeb. Thaum lub dov thickness loj, qhov kev sib cuag ntawm cov khoom siv thiab cov khoom siv tam sim no nce vim qhov tsis ua hauj lwm ntawm cov khoom siv yuav tsum tau dov nruj nreem, thiab lub zog sab hauv ntawm lub roj teeb nce. Tom qab lub roj teeb yog cycled, cov kab nrib pleb yog tsim nyob rau hauv qhov zoo electrode nto ntawm lub roj teeb nrog ib tug kuj tuab dov thickness, uas yuav ua rau kom cov kev tiv thaiv ntawm lub nto active khoom ntawm tus ncej thiab cov tam sim no collector.

Lub sijhawm hloov pauv ntawm tus ncej

Lub sijhawm txee sib txawv ntawm qhov zoo electrode muaj kev cuam tshuam ntau dua rau kev ua haujlwm sab hauv ntawm lub roj teeb. Thaum lub sij hawm txee luv luv, lub zog sab hauv ntawm lub roj teeb yuav nce qeeb vim cov nyhuv ntawm cov pa roj carbon txheej txheej ntawm cov lithium hlau phosphate thiab lithium hlau phosphate; Thaum lub roj teeb cia ntev ntev (ntau tshaj 23h), qhov kev tiv thaiv sab hauv ntawm lub roj teeb nce ntxiv vim muaj kev sib xyaw ua ke ntawm cov tshuaj tiv thaiv ntawm lithium hlau phosphate nrog dej thiab adhesion ntawm cov nplaum. Yog li ntawd, nws yog ib qho tsim nyog yuav tsum nruj me ntsis tswj lub sij hawm turnaround ntawm ncej pieces nyob rau hauv tiag tiag ntau lawm.

Kev txhaj tshuaj ua kua

Lub ionic conductivity ntawm cov electrolyte txiav txim siab nyob rau hauv lub tsis kam thiab tus nqi ntawm cov roj teeb. Lub conductivity ntawm cov electrolyte yog inversely proportional rau lub viscosity ntawm cov kuab tshuaj, thiab tseem cuam tshuam los ntawm cov concentration ntawm lithium ntsev thiab qhov luaj li cas ntawm anions. Ntxiv rau qhov kev tshawb fawb optimization ntawm cov conductivity, lub ntim ntim thiab lub sij hawm infiltration tom qab txhaj tshuaj kuj ncaj qha cuam tshuam rau sab hauv tsis kam ntawm lub roj teeb. Kev txhaj tshuaj me me lossis lub sijhawm infiltration tsis txaus yuav ua rau lub zog sab hauv ntawm lub roj teeb loj dhau, yog li cuam tshuam rau lub roj teeb Lub peev xwm ua si.

Kev cuam tshuam ntawm kev siv

kub

Qhov cuam tshuam ntawm qhov kub thiab txias ntawm lub internal kuj yog pom tseeb. Qhov ntsuas kub qis dua, qhov qeeb qeeb ntawm ion xa mus rau hauv lub roj teeb thiab ntau dua qhov kev tiv thaiv sab hauv ntawm lub roj teeb. Roj teeb impedance tuaj yeem muab faib ua ntau impedance, SEI membrane impedance, thiab them hloov impedance. Cov impedance thiab SEI membrane impedance feem ntau cuam tshuam los ntawm electrolyte ionic conductivity, thiab kev hloov pauv ntawm qhov kub thiab txias yog raws li qhov kev hloov pauv ntawm electrolyte conductivity. Piv nrog rau qhov nce ntawm ntau impedance thiab SEI zaj duab xis tsis kam ntawm qhov kub thiab txias, tus nqi tshuaj tiv thaiv impedance nce ntxiv nrog rau qhov kub thiab txias. Hauv qab -20 ° C, tus nqi them cov tshuaj tiv thaiv impedance suav txog yuav luag 100% ntawm cov roj teeb tag nrho sab hauv.

SOC

Thaum lub roj teeb nyob hauv SOC sib txawv, nws cov kev tiv thaiv sab hauv kuj sib txawv, tshwj xeeb tshaj yog DC sab hauv tsis kam ncaj qha cuam tshuam rau lub zog ua haujlwm ntawm lub roj teeb, thiab tom qab ntawd cuam tshuam cov roj teeb kev ua haujlwm hauv lub xeev tiag tiag: DC sab hauv tsis kam ntawm lithium roj teeb txawv nrog. Qhov tob ntawm qhov tso tawm DOD ntawm lub roj teeb Lub zog sab hauv yog qhov tsis hloov pauv hauv 10% ~ 80% tawm lub sijhawm. Feem ntau, qhov kev tiv thaiv sab hauv nce ntau ntawm qhov tso tawm qhov tob tob.

cia

Raws li lub sijhawm cia ntawm lithium-ion roj teeb nce, cov roj teeb tseem muaj hnub nyoog, thiab lawv cov kev tiv thaiv sab hauv tseem nce ntxiv. Ntau hom roj teeb lithium muaj qhov sib txawv ntawm kev hloov pauv hauv kev ua haujlwm sab hauv. Tom qab lub sijhawm ntev ntawm kev cia rau 9-10 lub hlis, qhov kev tiv thaiv sab hauv ntawm LFP roj teeb yog siab dua li ntawm NCA thiab NCM roj teeb. Qhov nce tus nqi ntawm kev tiv thaiv sab hauv yog cuam tshuam nrog lub sijhawm cia, cia kub thiab cia SOC

lub voj voog

Txawm hais tias nws yog kev cia lossis kev caij tsheb kauj vab, qhov kub thiab txias muaj qhov cuam tshuam zoo ib yam ntawm cov roj teeb sab hauv. Qhov siab dua qhov kub ntawm lub voj voog, qhov ntau dua qhov nce ntawm kev tiv thaiv sab hauv. Kev sib txawv ntawm lub voj voog sib txawv muaj qhov sib txawv ntawm qhov ua haujlwm sab hauv ntawm lub roj teeb. Internal resistance ntawm lub roj teeb nce nrog qhov nce ntawm qhov tob ntawm tus nqi thiab tawm, thiab qhov nce ntawm cov kev tiv thaiv sab hauv yog proportional rau qhov nce ntawm qhov tob ntawm tus nqi thiab tawm. Ntxiv nrog rau qhov cuam tshuam ntawm qhov tob ntawm tus nqi thiab tawm hauv lub voj voog, tus nqi txiav tawm hluav taws xob kuj tseem muaj qhov cuam tshuam: qhov qis dhau lossis siab dhau qhov txwv ntawm tus nqi hluav taws xob yuav ua rau muaj qhov cuam tshuam ntawm cov electrode, thiab ib qho passivation zaj duab xis tsis tuaj yeem tsim tau zoo nyob rau hauv qhov qis qis qis qis qis, thiab siab dhau qhov ntsuas hluav taws xob sab sauv yuav ua rau cov electrolyte oxidize thiab decompose rau ntawm qhov chaw ntawm LiFePO4 electrode los tsim cov khoom uas tsis tshua muaj hluav taws xob conductivity.

lwm yam

Lub tsheb-mounted lithium roj teeb yuav inevitably muaj kev tsis zoo ntawm txoj kev nyob rau hauv cov kev siv, tab sis cov kev tshawb fawb tau pom tias lub vibration ib puag ncig ntawm lithium roj teeb yuav luag tsis muaj kev cuam tshuam rau sab hauv ntawm lub lithium roj teeb thaum lub sij hawm daim ntawv thov.

Outlook

Internal resistance yog ib qho tseem ceeb rau kev ntsuas lithium-ion fais fab kev ua tau zoo thiab ntsuas lub roj teeb lub neej. Qhov loj dua qhov kev tiv thaiv sab hauv, qhov ua tau zoo ntawm lub roj teeb, thiab qhov ceev nws nce thaum khaws cia thiab rov ua dua. Cov kev tiv thaiv sab hauv muaj feem xyuam nrog cov qauv roj teeb, cov khoom siv roj teeb thiab cov txheej txheem tsim khoom, thiab kev hloov pauv nrog kev hloov pauv ntawm qhov kub thiab txias ntawm lub xeev. Yog li ntawd, txoj kev loj hlob ntawm cov roj teeb uas tsis muaj zog sab hauv yog tus yuam sij rau kev txhim kho roj teeb lub zog ua haujlwm, thiab tib lub sijhawm, kev paub txog kev hloov cov cai ntawm cov roj teeb sab hauv kuj tseem ceeb heev rau kev kwv yees lub roj teeb lub neej.